You can only use AA miles to upgrade on CX flights based on full Y fares. Cathay Pacific's Asiamiles and Swissair's Qualiflyer program are the only programmes which you can upgrade on any economy class fare.
There really isn't any sure way to use miles to upgrade a fare to Australia on OneWorld airlines. Best is to buy an economy class ticket and hope for an operational upgrade if you have status.
[This message has been edited by Guy Betsy (edited 06-27-2001).]