New Orleans Public Belt

A recent news photo shows a group of people, descendants of Homer Plessy and of Justice Harlan, the only dissenting judge in Plessy v. Ferguson, standing in front of a heavyweight, open-platform business car lettered New Orleans Public Belt; the number is not visible. I had no idea the NOPB had a business car -- anybody know something about it? The windows indicate that the car was rehabbed sometime after WWII, but the regular spacing of the windows suggests an interior configuration unlike the usual business car.