The electric utility companies sign delivery contracts with the RRs. Some own their own trains of hopper cars and some lease same. The amount of coal needed is based on power generating needs. Some power plants such as the NPPD Gerald Gentleman II station near Sutherland, NE has its own traffic manager who basically controls the coal train traffic into the plant. He is in constant communication with the RR as to the location of each of his trains and can hold trains at the plant or inform the RR to hold a train outside the plant.
Worked a terminal that serviced two large generating stations. In the early 1980s a RR crew unloaded trains at the plants. Later, one plant began to unload their own trains. The other plant still utilizes RR crews to unload the trains, at least as of late 2002. Trains are unloaded automatically via rotary dumper and machinery that pulls the entire train along and spots each car for unloading.
Worked the PRB for several years, as well. In the early 1980s the RR had a loading pool that loaded all trains at the various mines. As a cost-cutting measure, by 1986 road crews loaded their own trains, insuring 12+ hour days (the deadhead home did not count as "service"). By the early 1990s the loading pool was resumed, but road crews continued to load trains until relieved. In the late 1990s the mines began to hire non-union loading crews via a contractor. I believe that all mines now have contract loading in the PRB, but I have been away since 2000.
Coal trains out of the PRB on the Orin Line East get inspected at Guernsey, WY. Same for hopper (empty) trains going west up the Orin Line. Coal trains going west on the Orin Line and then east through Edgemont, SD are inspected at Alliance, NE and the same for westbound hopper trains.
Coal trains departing the various mines must receive permission from the dispatcher to do so. All the lines I once worked are CTC and train movement is authorized by signal indication.