My verdict: The marketing tactics notwithstanding, this is not an intentionally Christian film. You can certainly find parallels if you look for them , but the filmmakers had no such intentions. They utilize several Christmas songs in the sound track—but none of them reference Jesus Christ. They talk guardedly about the 'spirit of Christmas' (as represented by Santa and one of the bells from his sleigh). If they're alluding to Jesus Christ, it's unfortunate that the soundtrack is so devoid of carols that reference Christ. If they're alluding to anything else (e.g. "giving"), then I have no idea why they went on and on about believing and were so unwilling to name the theme outright.
A few other complaints:
- All the troubles on the train (lost ticket, Flattop Tunnel, the gulch, ice on the tracks, caribou, broken headlight, etc.) don't move the narrative along. It seems like they're all tacked on to make the movie longer.
- The characters all look a little creepy—mainly because of their eyes and teeth (especially the black girl).
- Every one of Tom Hanks' characters sounded like…Tom Hanks.
- The so-called know-it-all didn't sound like a kid at all; he sounded like an adult doing a very poor job at imitating a kid.
 See http://en.wikipedia.org/wiki/Evangelicalism#Adherents.
 They've also been responsible for marketing The Passion of the Christ, the Chronicles of Narnia film series, Expelled: No Intelligence Allowed, etc. See http://moviemarketing.biz/.
 See http://www.slate.com/articles/news and politics/hey wait a minute/2004/12/next stop bethlehem.html.
 See http://christiananswers.net/spotlight/movies/2004/thepolarexpress.html.
 See www.slate.com, loc. cit.
 Even less congruous, there is an appearance by Steve Tyler, voiced by himsElf, in a band, performing a very un-Christmasy song.
 The closest they get is "Good King Wenceslas", which is technically a Boxing Day carol.
Train in the Snow is by Evelyn Simak, available at http://commons.wikimedia.org/wiki/File:LNER A4 Class 4-6-2 No 60019 Bittern - geograph.org.uk - 1625914.jpg.