According to A300Man the wet-leased A330 will be needed for Australia services. Range is DOH-KUL is about 3300nm and KUL-SYD is about 3650nm I don't know if EI's A333 be able to do the 3650nm trip with full cargo loads since they are not the 233t MTOW variant so if QR wants to fly the A330 to SYD the A330-200 would be needed. As with PTV's I don't think they will be an issue as QR's A300 don't have them.
BD also have an A330-200 to spare and it won't matter that they use RR engines since in a conventional Wet Lease deal all maintanence is done by the lessor, but that would mean BD would have to have Trent 700 certified Tech Support available in DOH in case of engine problems which will lead to increased costs.
The A330-200 CF6 operators are:
Air France
Qatar Airways
Volare Airlines
Aer Lingus
TAM Brasil
I can think only of TAM and Volare who are able to provide capacity.
There are also two parked CF6 A330-200's which are ex-Canada3000.