So I was looking at doing this as well... apparently, there are only 2 examiners who can do fixed wing ATPL tests outside of the airlines. One is in BNE and the other is in Melbourne. CASA's response when I asked if I could do my ATPL test as part of my recurrent at CAE Dallas was "yeah, shouldn't be a problem." While TECHNICALLY correct, their answer is FACTUALLY incorrect and seriously disingenuous. If you want the examiner to come out of the country, YOU will be paying for their travel, accommodation, and testing fees while outside of Aus.
In the end, the math dictates that you do the $12,800 course at BNE in the silly citation.
CASA kinda sucks.