I agree with pennsyk4. I have always seen business cars at the end of a train. They had restricted access (like RPO cars), and coupling them to the end suited that. At their destinations, they could easily be uncoupled and spotted where necessary.
A variation would be an Office Car Special (OCS). Several business/private cars are run as an extra. NS and the Reading & Northern run them in this neck of the woods. For a while, Conrail stored an OCS consist at The Reading Shops.
On a road as big as the Pennsy, anything is possible. But running a business car by itself as an extra would require dispatchers to schedule traffic around or past it.
Returning home from New Orleans on Amtrak's CRESCENT LIMITED, I noticed our train was entering a passing siding. After a freight passed, the engineer whistled off and our train BACKED UP! "What's going on here?" I thought. Back on the main, we went forward. Then we passed a short freight (probably a local) on the passing siding. The dispatcher put our train and that one head-to-head on that siding. I have always admired that maneuver.