SOPS, Australian law overrides company SOPs. So your pilots are guilty if they obey your company SOPs and erase a CVR at the end of a flight and thereby impede an Investigation - even an Investigation which has not yet commenced (see Section 24).
You ask whether QANTAS is exempt. I can only imagine it is. Unless there is some secret MoU (Memorandum of Understanding) or suchlike which restricts the way this legislation will be applied to QANTAS and its crews, they would be screaming. Perhaps a QANTAS pilot can tell us?
I am not a lawyer but I think the safe course is to turn off your CVR before entering Australian airspace.
However you should be aware that you are still liable to 6 months' jail if you do not turn the CVR back on immediately there has been an "immediately reportable incident". Why not? Because Section 24(5) says "In this section, conduct includes omission". Neat, huh?
In Australia, the CVR is going to become a fully-fledged weapon of attack against crew members if this Bill becomes law.