- A cab1 remote- transmits 27MHz.
- A cab1 base receives 27MHz and retransmits 455 KHz TMCC.
- An early TMCC Powermaster receives 27Mhz directly from either a CAB1 remote, or a Powermaster bridge- receives 455KHz, retransmits 27MHz.
- A Legacy Powermaster receives 455KHz TMCC/Legacy
So in your scenario- no, a CAB1 remote will not "directly" talk to a Legacy Powermaster.
If you have both a CAB1 remote and CAB1 base- then the remote talks to the base and the base talks to the Legacy Powermaster.