How does Shambhala differ from traditional Vajrayana Buddhism as it is practiced in Asia? How is Shambhala Buddhism as founded by Chögyam Trungpa Rinpoche and continued by folks like Pema Chodron different from traditional Tantric Buddhism such as that practiced by the Dalai Lama?  Does Shambhala rely on the same texts as Tibetan Buddhism?
In the editor's preface of my copy of Trungpa's 'Shambhala - The Sacred Path of the Warrior' it is claimed (and I do well agree with that), that the Shambhala teaching is "a major departure" from Trungpa's earlier, popular but quite orthodox Tibetan Buddhist books. This is further elaborated, saying that the outlook is rather secular than religious and in the broadest possible way universally-human.

This fits quite well with my personal impression of the teaching, that it tries to avoid anything too specifically buddhist, too 'sectarian', too foreign (for westerners), too 'exotic', but rather attempts to - if I may say so - lead westerners (that unmistakably are the audience talked to) back to a common human source of dignity rather than providing yet another foreign source of 'spirituality' to draw from.

This also means, that it does not rely on any scriptural source, rather - in a rather unimportant and personal way - it relies on the tradition of the Shambhala kingdom.