
All you can do is drive back and forth on ~40 miles of Route. ( Yes, I have completed all scenarios and services)
There is one scenario that lets you "Free to Play" but you are limited to the yard. In all cases there is very few static cars available to switch. Most all cars are part of consist scripted for service.
[youtube]http://www.youtube.com/watch?v=xuP6KCp8RFE&t=203s [/youtube]
https://www.youtube.com/watch?v=xuP6KCp8RFE&t=203s