speeeedy,
I don't think the ATPL requirements change because of the AOC of your employer.
Actually they do vary depending on High Capacity or Low Capacity.
Requirements for command hours are less under a High Capacity AOC that has a CASA approved C&T cyclic training program.
Isn't 500 hours PIC required for an ATPL?
The ATPL requirement is for 250hrs PIC which may include up to 150 hours acting in command under supervision.
This can be achieved on any aircraft type and
does not need to be multi engine.
Therefore it is not a CAO requirement for QF, J* or DJ to have a 500hr PIC requirement as they are all High Capacity AOC operators.
As others have pointed out other factors such as insurance companies may come into play.