Trains are one of the few surviving and functioning artifacts Human post Apocolypse technology. These vehicles where used to transport passengers and goods before the Apocolypse.
-It is possible that the armies of Omegatronics and/or Alphetekk used these to transport their robot soldiers and Guardians.
-At least three where know to be still functioning, and all serve as a stages for Epoch.
-Epoch has hitched rides on them to reach the second Cryogenics building and a Power Core