T Equipment and Ayer Questions for the Late 1970s

I have been messing around with Dustin era N scale equipment. Several of my fellow club members have been getting involved with T Trak modules. My idea is to do one of Ayer. This has lead to a few questions. I hope that my friends here can help.

First, I know that the Ayer interlocking was simplified, due to the 4R project, and am aware that it happened in my era. The other day I found a Youtube video, which was somewhat earlier. The local power, a GP7 was parked on the Hollis Branch (WN&P). When was the switch from West Main, to the Hollis Branch removed?

My second question has to do with equipment. The Budds ended self propelled service after the 1978 blizzard. After that, they were towed by either B&M, or MBTA geeps. How common was this compared to the Boise Budds, or even the newer coaches? Did the train size dictate whether a few Budds were towed, or push-pull equipment was used? When the push-pull equipment was used, did consist size have much to do with either F10, or F40 assignment?

I just want to run a believable consist for the era.

In partial response to your equipment questions, I've posted three photos from the early '80s when B&M/GRS was operating the entire MBTA showing:
1. An F40 pulling 4 Boise Budds (or noisy Budds as their trucks made a lot of racket!) departing W Natick.
2. An F40 pushing three PS (?) coaches with a demotored RDC used as a cab car at Ayer
3. An F10 pulling 5 RDCs toward South station at Natick on the Framingham line

Wow, those Boise Budds look pretty sharp. I like their design far better than any of the flats the MBTA currently has.

Anything with fluted stainless steel and big windows gets my vote!