QBE I think, which was what it was rego'd with before I bought it.
It's CTP, pray that you never have need to use it. Otherwise, price wise there's f' all difference between them.
If you're an RACQ member, then the $10 discount you get for going with RACQ (edit: The discount is on the membership, not the CTP, still it's $10) I'm pretty sure still makes it them cheapest. So yeah, $10 bucks, just as a idea of how little difference there is between them.