When the two trains are approaching, the leader of the terrorist group is shown emerging from the back door of a passenger car to view the stopped train in the middle of the bridge ahead of them. The only problem is, the train on the tracks ahead of them can only be seen from the locomotive at the front of the train. To make matters worse, the terrorist leader was going out the BACK DOOR of the car, so he was looking in the opposite direction. Not only could he not see the train straight ahead from anywhere but the locomotive, but he wasn't even facing the correct direction to see it.
When the Delta operatives breach the train, one of them crashes through a window carrying a large automatic weapon, not the kind you bust through a small window with, nor the kind Delta uses in close quarters.
Just before the terrorist's train contacts the empty blocking train on the bridge in it's attempt to push it back, the blocking train puts power to the wheels and begins backing up, although it isn't supposed to have anyone in it. Steam is clearly visible escaping from the drive system under the locomotive.