The Regionals should always be consistent, as those trains have to be physically turned around using either a wye track or a loop track. I just don't ride them very often, so I couldn't recall if BC was always right behind the engine or not. Or maybe it was also the influence of the wine with dinner.

Acela is a different situation, as that train can be operated from either end. In Boston & DC, they basically just clean it and then change ends for the next run. However, in NY, all Acela's that terminate there, run out to Sunnyside yard and go around the loop track to the yard. It's for that reason that Amtrak cannot consistently have the FC car on the same end.