For a couple months in 1977, just before the end of all MP54s on Conrail's commuter lines, a pair of the old cars replaced the normal Jersey Arrow on the Princeton Dinky (aka PJ & B - Princeton Junction and Back).
The three biggest passenger carriers - Pennsylvania, New York Central, and New Haven - merged to create the ill-fated Penn Central, whose passenger losses and poor service led to the formation of Amtrak and state-owned commuter lines.
Thanks largely to mergers and bankruptcies, New Jersey's commuter railroads underwent profound changes between the end of steam and the takeover by NJ Transit in 1983.