The original gray CAB-1 can control the original gray PowerMaster, can be set in conventional mode, can control MTH PS1, PS2, PS3 in conventional mode. Would not recommend you purchase this setup going forward. In 1999, it was a good idea. The original gray PowerMaster listens to CAB1 26MHz only, the newer blue PowerMaster listens to 455 kHz TMCC track signal from any of the command bases.
Should point out I never did that. I have
- controlled some Lionel postwar engine with original gray PM
- controlled some MTH PS2 CTA set with IC Controls TPC 3000, in conv mode. Worked pretty good. (TPC units listen to serial data, 9600 Baud wired)
- controlled MTC IC E9 PS2 set with blue PowerMaster in conv mode, with blue CAB-1L.
I do not recall ever controlling an MTH PS2 or PS3 engine with the gray one. (Its actually more black).
Highly personal opinion - if you are tight for $, don't buy any control system, just run conventional at the current time.