Australian banks are not right now supporting Apple Pay for the simple fact that they don't need to.
Unlike America, Australian banks had/have great support for NFC debit/credit cards. You walk into virtually any retailer in Australia and there is an extremely high chance that their eftpos machine supports 'Tap and Go'.
So basically, Australian banks don't need Apple's assistance in getting NFC out into the general population and thus don't need to give apple any 'cut' of their revenue.
On a personal note I have this 'tag' stuck on the back of my iPhone which is available from commonwealth bank. It is a NFC tap and go tag. In the commbank app you can select which account the tag is linked to, withdraw money from an atm with out having to have a real card with you. You can also active /deactivate the card through the app.