I also saw and enjoyed the movie and when I was in Chicago recently I also traveled on the Metra out to Waukegan and back (purely for the trip not because there was anything there I wanted to see or do).
Interesting double decked commuter trains you have in the US - the upper deck with the "hollow" centre isle, the single centre entry/exit door and the steps down to the low level platforms are all totally different to the double decked commuter trains we here here in Sydney.
I have no info on where you can find Metra units for Trainz but I thought you would appreciate at least one response to your post.
Peter Ware