I imagine some railroads must acquire their ballast from off-road sources. If so, would they send their own ballast cars to be loaded there, or have the ballast delivered in regular hoppers by the connecting road?
I ask because MOW equipment is often old, and thus never leaves the home road. I've noticed that many ballast cars have roller bearing trucks however, so I'm picturing them being interchanged in regular freight traffic. Is this a normal practice, or would it be the exception?
TIA Mac B.