I saw this post and since its still going on, I'd just chime in here...
Out of all movie scenes with steam, I'd have to say my favorites would be the Sierra #3 in BTTF Part 3, its last major film. Probably because this is one of my favorite locomotives and the scene was pretty good. Second would be the B&O William Mason in "Wild Wild West". It looked beautiful in the green paint. I don't know if it still wears "wanderer" paint, but it did for awhile. Strasburg (Linn Moedinger, not Uhrich) did the rebuild on that. Restoring 19th century locomotives that haven't operated in decades...to operation...is not an easy task and is a great accomplishment showing great skill. I haven't done it of course but I can just imagine...picture Eureka in the 80s after the Old Vegas fire and then picture it now.
That movie also has shots of the JW Bowker and the "Reno", which were not steamed of course due to the fact that one has an iron boiler, and the other one was in a major fire, and neither operate anymore.
-Ed Kelley