CSX's isolated line from Port Huron to Marysville is pretty much solvency dependent on propane. They run empty from Flint to P. Huron every other day, and return with anywhere from 10-50 loaded the opposite days. (trackage rights on CN between Flint/Port Huron). Of course, there are some other commodities handled, including occasional unit coal trains, but, propane is the staple. Seems to me, a railroad would be happy to handle any type of load, as long as the cars the shipment is on are free of defects.