I don't know for sure but I'd imagine every railroad car has a designated A and B end. If for no other reason, it needs to have one to ID which end you're talking about ("Hey the work order says replace the coupler, but which one? They both look okay!").
As for cabooses (cabeese?), I couldn't imagine a crew would give any thought to which direction it was turned, just so long as it was in the right position within the train itself.
The funny thing is my wife, who is not a train fan (but tolerates my interest in that as well as other things) says she really misses them on the backs of trains as when she was younger, the crews would often wave and she missed that...
