Read this stuff dude:
http://www.railroad.net/forums/viewtopic.php?t=27934
If a car rolled out on a piece of track in between control points, and there wasnt a train already in there, the dispatcher would see something pop in/up on that stretch of track.
CP001................the car just rolled out at MP 005....---->.......CP010
Once it passed CP010 then they would know that something is out there and moving. If it never moved past CP010 the train dispatcher wouldnt know what was out there....broken rail, switch open, wet track, car rolled out.....
CAD keeps track of the trains as they approach and leave control points. Train dispatchers just make requests.