Why Source Code did indeed create an Alternate Reality

4.  Is the ending a new "movie reality" (for lack of a better term)?  Why or why not?  Is it possible that Stevens' determination somehow merged the alternate universe with the movie's original reality?
I believe the ending is a new "movie reality" because the events resemble a time-line where the teacher (don't remember his name) stopped the anarchist cold, completely denying his attempt to "remake the world". I don't really believe that any one man's determination could actually break down the barrier between parallel universes. However I do believe that the instant Captain Stevens decided that he could and was going to save everyone that was on that train, as he contemplated the idea, the alternate universe was created. In the end, within the Source Code, he took the place of the teacher and, as he had no place to return to in the "real world", he was allowed to remain within said parallel universe.
Of course, there is always the alternative that the Source Code program was much more complex than what Rutledge let on, regardless of whethere he was aware of it or not and was capable of simulating not only the events that originally occurred but seemingly allowing for random occurrences, including how Stevens was capable of completely affecting everything that happened, finding the killer even though the teacher didn't know who it was. If Rutledge didn't exactly know the extent of his program, then it would seem to suggest a Singularity, an AI which is more intelligent and creative than a human being and capable of upgrading itself. However, Occam's Razor would seem to suggest that this is even more unlikely than the previous hypothesis.