Charlie Foxtrot India
You don’t need to have an ATPL to hold a P1 rating on something like a Metro or even a B747 for that matter in RPT ops. The only restriction is you can’t be in command. You can log ICUS or P1US though which you would do every time you are pilot flying. When you are pilot not flying you log P2.
poorlypaidpilot
You will find that CAR 5.173 (2) states that of the 250 hours command required for the issue of an Australian ATPL, 150 hours of it can be ICUS.