I don't know. But it makes me highly suspicious about the rocket launcher found near the tracks in Atlanta. May be more to that story as well.
it was a wireless device..... you could just have someone place a knapsack 100 yards down the line near the tracks, the train trips the wireless device, the knapsack blows up, the track in broken, you derail the train before they have time to stop.....
you dont want to break a rail prior to the train arriving because the signals will all turn red. (there is a small current that runs through rails on most territories...if the current is interrupted, the signals all go red)