Cool! I remember seeing that long, long ago. It must have been on the school field trip to the National Film Board in Montreal. I might also have seen it on CBC TV. There are some nice cameos of CN locos in there, and right from the start, a MLW FPA-4!
Keaton made a bunch of movies starring trains. https://www.trainboard.com/highball/index.php?threads/any-other-buster-keaton-fans-here.60115/