3 years ago a bird breeder i used to know was in darwin and had visited a big time exotic bird breeder that had some. Didnt elaborate on where in darwin but said he had def seen them. I see no reason to disbelieve him. In the early 2000's military, hyacinth, greenwing macaws were all the same way. The popularity of large birds in homes as pets took of and they were mass bred and are now more common. As well as illegal import of eggs helps as well. So its very possible that there is a decent population here in private hands.