How long the assignment was for I don't know since I rode the train only once, but in the Summer of 1958 or '59 there was an E-7(number unrecorded)-hauled local out of Springfield to Greenfield that hauled onto the Loop and backed Fitchburg Division to Greenfield. Supposedly, the train was then to go local to North Station. If that's the case, then there would have been a Boston-Springfield RT loco-hauled train for at least a short period, whether it was under two numbers or four. Mebbe someone's got a public or ETT for the period for better documentation than my semi-century-plus memories.
We got off at Greenfield, explored East Deerfield, and took the afternoon Budds back to North Station. Budds could book.
"A gray crossover is definitely not company transportation."