All of the cab control cars when delivered new were equipped with cab signals as well (including the RDC's - "Boise Budds" rebuilt into unpowered coaches by Morrison Knudson).
From memory, this is a historical look at road power used by the T that didn't have cab signals.
- All B&M RDC's except one (6124?; this one was used frequently on the Shore Line)
- All leased GO cab control cars (one set did run in Providence service but was "top-and-tailed" with FP10's)
- The D&H PA's (used mostly on the Framingham; they were used on Providence runs trailing E8's)
- The B&M GP-7's leased for the North Side service or B&M GP-9's used on the Framingham Line and possibly the Needham Line in '77-'78.
- MBTA RDC 55 which was originally NYC M455; as I recall, Penn Central moved this car from Ann Arbor/Detroit service to Boston when the former was annulled. It ran on the Needham line until that line was closed for the SW corridor construction and the Framingham Line, then used on the Back Bay shuttle or in the middle of a consist with cab signal equipped RDC's. I was surprised to see it in the middle of a consist in Sharon during the early summer of 1980.
- All of the SEPTA, NJTransit and Canadian Pacific RDC's acquired second hand or leased.
The Franklin and Stoughton Line trains needed cab signal equipment because these trains run on the Shore Line to get to the branches. Framingham and Needham trains did not. Needham trains would typically run on Track 3 to Forest Hills which wasn't equipped with cab signals back then.
When the SW Corridor was under constructions, trains were re-routed for 9 years over the current Fairmont Line. This line got cab signals for the first time when rehabbed for this service.
Speaking of historic South Side equipment restrictions, trains equipped with Pullman Standard push pull equipment (now the "200's") were limited to 30MPH while passing under the Washington St overpass in Dorchester in both directions as well as Canton Viaduct, track 1, due to clearance issues.