There is no tourney format and hasn't been for the past few years. No other countries have really bothered to compete in the past few events, so it's devolved to a glorified series of exhibition games between Australia and NZ where both teams already are qualified to go to the world event (Olympics, WC).
It's been a complete farce that FIBA has let this go on as long as it has and I'm happy they finally got their heads out of their asses and merged Oceania into FIBA Asia for the next event.