Just a new Locomotive for San Andreas, including carriage. New models and COLs, so you can walk around in it, even when the train is driving. You can also walk into the locomotive itself, but to enter it as a driver you need to stand outside the locomotive, and then enter.

Oh, there's also a movie on YouTube, check it:

http://nl.youtube.com/watch?v=KLEaiOV-Iiw

Enjoy!