When 'carload' figures are quoted in the industry they are always referring to 'revenue' carloads, or loaded cars. So, if a line is said to do 3,000 carloads a year that would be only counting loaded interchanges. So, if it was all outbound lumber, for example, there would be 3,000 empty cars moving in from interchange to shipper and those same 3,000 moving out. So, dividing the carload count you were given for the POTB would be incorrect.

While I don't believe the POTB handles 286k lb cars, they certainly handle 263k loads, which makes the usual 4 truckload comparison valid. Those centerbeam (A-frame if you speak 'Burlingtonese') flats are fully loaded.