It is a slightly complicated argument, but there are a number of points. First of all, her view is entirely biblical in its grounding, as here when she answered further questions in Pittsburgh, according to Episcopal Life Online:
...she has noted in the past that "most Christians believe Christ died for all, as saviour for the whole world."
She said she has also cited the Bible's record of God's promises to the Jewish people and other promises that "were not broken by Jesus' life, death and resurrection."
"Therefore, Jews have access to salvation without consciously saying 'Jesus is my Lord and saviour.' I didn't do that; God did it. I also see that God made promises to Hagar and Ishmael, whom Muslims claim as their ancestor," she said. "I don't think God broke those promises when Jesus came among us."
Jefferts Schori had touched on the question during her sermon, noting that "Episcopalians and other Christians wrestle with how broadly to understand the family of God, and whether non-Christians are included, for we can certainly point to holy examples who show us what God at work in the world looks like -- people like the Dalai Lama and Mahatma Gandhi."
As a child I rarely attended any church and had no religious upbringing, except what was learnt at school. At my schools the impression given was that Judaism was an old religion that had finished, and it had been replaced by Christianity. I was surprised when I learnt that there were still people following the old religion, and of course I grew up when I learnt about reform movements and conservative movements etc.. Before and during the rise of a counter-nationalism, Judaism in Germany was a progressive force and fully part of its intellectual life; some Jews would have converted to a liberal and open Protestantism as part of that progressive trend. Germany then turned into empire seeking and then fascism, the very opposite of what it had been.
Regarding Judaism, then, clearly there are Covenants and promises within the Biblical text and it would depend whether one has Luther's replacement theology or a tree and branches theology. Some of today's most right wing Christians have adopted something like the latter, as it suits their right wing pro-Israel stance and almost crazed last days expectation - giving divine history a push via conflict. This, though, is only a transitory support for Judaism, and most religious Jews would be wise to keep away from this ritual-copying theft. However, on a more moderate and less messianic front, there are indeed promises regarding salvation in the Hebrew Bible, and it is a matter of opinion whether these are superseded or not.
The matter of Ishmael and Hagar is also biblical, but if this goes on to apply to Muslims into the future (rather than Jews from the past going forward), then there are problems. There is no historical evidence for the existence of an Abraham at all, and it's a mythology, but the early Christians would have seen him as a key patriarch as they learnt from Judaism - and indeed many were Jews initially. The Qur'an, however, is a mythology applied to that mythology - the mythology that Abraham ever established the Ka'aba and that it subsequently became paganised that Muhammad then rescued on receiving the transcript of the Qur'an. Whereas the Jewish myth is attached to the Christian myth, the Islamic is not, and is so only from its point of view. Its view of Christianity - that Isa wrote the Book perfectly but it was corrupted into the New Testament - is clearly an anti-historical view regarding the Rabbi Jesus and nothing to do with the doctrines established after Paul and in the general stream of Christianity.
Otherwise one may as well look in the biblical texts and construct the view that Baha'u'llah is a messiah for this age for some. That clearly is a very pluralist view of salvation and the means to it via manifestations of God. The Baha'i Faith misrepresents and misunderstands Christianity as a tradition on a number of points; it is its own interpretation of Christianity, as it makes rough interpretations of Hinduism and Buddhism that their faithful would not accept. So it does not make sense that way around.
She further makes references to God at work, as in the Dalai Lama and Gandhi. Now I have a sympathy and a sort of agreement with this viewpoint, but the Dalai Lama would reject as a principle that he shows any God at work, and Gandhi specifically wanted no following as would be generated as if he were a manifestation of God. From a Christian point of view they must be reflecting some sort of divinity via their holiness, but it may have no salvic impact. Bishop Jefferts Schorri is not claiming that they do have any salvic impact, though in leaving it all to God she is not denying the potential.
Her view is clearly biblical, and extended according to like holy behaviour. However, this ought to come with a warning. The English Presbyterians and some American Congregationalists decided to be fully and completely biblical, but specifically rejected doctrines and articles as binding. In other words, there were no rules as to how the Bible was read. The two groups, and the new ideological and capitalist liberals in these groups, realised in their selective literalism that the Bible contained no doctrine of the Trinity. Jesus in the synoptic gospels gets a kind of earned divinity with a puzzle as to whether he already has it, and the denouement is his resurrection by God - the affirmation of his place as Son of God. John's gospel has Jesus as divine from the beginning and yet has subordinate elements, which equates to Arianism. The Socinians in Poland were humanist Arians - Jesus was divine and human, but fully human and less divine than God, and they were selective literalists who believed in everyone reading the Bible according to ordinary comprehension. They too saw no doctrine of the Trinity. The Transylvanian Unitarians took a more radical view than Faustus Socinus, and they too had a Master Jesus but one who was fully human and whose divinity could be achieved (but hardly likely - holiness equates to divinity) by any one who followed his path.
My point is that the biblical route guarantees nothing. All these Conservative Evangelicals read their Bibles through doctrinal blinkers - this is why they are selective literalists - and they come to the Bible from outside. The few trinity-like statements that are late baptismal and Paul's doxology are simply the existence and functioning of God and Christ's place in connection with this work. The Socinians and Unitarians read and understood these passages as clearly as we do, except they did understand them without the later doctrinal developments of believers and Church Councils. You could read the Bible for yourself via ordinary comprehension.
It was only the later nineteenth century Unitarians (in Britain and less so the USA) that took in German biblical criticism and historical research, and who subsequently made a shift to individualism and subjective conscience as the main decider of religious beliefs rather than the Book. The earlier Unitarians (like Priestley) were believers in the Christ who performed miracles and was resurrected - because this was the work of God. They too used the language of the Holy Spirit as God inspiring and motivating.
So the fact that something is biblical is neither here nor there when it comes to Christian exclusivity and the Trinity. That has to be constructed as extra-biblical doctrine.The question regarding Bishop Jefferts Schorri is whether she believes in God the Father, God the Son and God the Holy Spirit as a threefold guide and as her grounding in spirituality. The Reformation Arians and Unitarians did not, and I see no reason to doubt that she does. However, she sees promises elsewhere and holiness elsewhere that does chip away exclusivity, and exclusivity is often paraded to be like pregnancy - either you are pregnant or you are not. It is a one or a zero.But it is not clear that this is the basis of Christian exclusivity, because clearly it sees divinity in the Saints without compromising its trinitarian doctrine. In the end, the issue is the salvation one in that to depend on Saints and their holiness is to depend on Christ, and something of this would have to be said regarding the Dalai Lama and Gandhi - the question being, how Christlike are they and how do they lead towards Christ?
My view is that this is not good enough, and I am a pluralist when it comes to all these various prophetic figures known and unknown. Jesus makes sense in a Jewish and subsequently Greek and Western sense, and other cultures can relate themselves to these and the blinkering of the biblical narratives. But each important religious figure can only be understood fully in their own context. Gandhi, as a modernist Hindu, has qualities that Jesus did not possess, and a different outlook. It does violence to him to just set him up as a channel only towards Christ. The same is true regarding the Dalai Lama: the Dalai Lama does not manifest God, because God is not part of the Buddhist way, and of course by extension Buddha is no forerunner of Baha'u'llah either. They are different and remain different. In that some of one religion can be jigsawed with some aspects of another religion produces a variation, a mongrel that might suit one individual or group but is not higher. It makes for something new.
My guess is that Bishop Jefferts Schori herself coheres in the Trinity and is an inclusivist, seeing holiness beyond the tribe and a Christian view of God who chooses whom to save, as well as the God who made promises in the Judaeo-Christian scriptures. To be a pluralist in any sense would be different from this. She is, though, quite clearly biblical, but that gives a range of options.
Of course a Presiding Bishop a Church does not make: even if she is pluralist as an individual it does not rewrite the Church and its doctrines, as does not the Archbishop of Canterbury's narrative style theology become an imposition on the Church of England (south).