Sounds simple...
During preflight the Captain decides whether he will be the PF or PM for the sector or whether the F/O will be PM or PF.
In case of One Engine Taxi Out (OETD), the PF will be the PT and the PM will be the PNT.
Once the dead engine is supposed to be started, the PT, as the PF will become the PNT and starts the engine, while the PNT takes over as PT.
Once the engine has been started the PNT becomes the PT again, and the PT reverts to being PNT, until at takeoff when the PT becomes PF and the PNT becomes PM.
There should be no confusion about this.
Coupled with a certain Big Airlines pilot switching roles this becomes interesting.
Now lets try to fit CM1 and CM2 into this
Caveat: Not an Airbus pilot.