Two or three different RR scenes in "How the West was won. Also another shot of Lizard head in the background of a wagon train scene. The Scene with the derailing cars was shot with some old V&T equipment owned by Paramount. There is another scene with the V&T 11 Reno with some studio built coaches on flatcars. This was shot on a spur built in Rapid City South Dakota for the movie. This is during the Transcontinental railroad scene when the Buffalo stampede takes place.
(Info from Larry Jensen's "Movie Railroads")
BTW that train robbery gunfight and wreck scene was an amazing piece of fimmmaking. I doubt we will ever see that again from Hollywood. Museums won't let it happen either. Also you can use computers to do so many more effects these days.
Jake Johnson