This is not an answer, but a minor contribution to help find similar units and references.

I've seen a similar controller from Mitsubishi called PAR21-MAA. it could to share the name of other similar controllers, at least it will help find contributors.

Indeed it operates on 12V on single wire - there is no polarity on connection as indicated in the installation manual. Since it also provides power to run the controller, the communication is so-called parasitic communication. a similar system is used by dallas chips, the most famous being ds18b20.

Mitsubishi provides a bridge from 5-wire CN105 to a single wire system called m-net. In m-net system, each unit has an address 01-50.

I suppose this means that the main outdoor unit has address 0.