Low Pass - If you re-read my post you'll see I said that pilots obtain a US ATPL (not JAR) to 'bypass' the Aussie ATPL.
In regards to the question - Why would you resit the aussie ATPL exams?
The scenario that I have seen had an aussie pilot go overseas to get an ATPL in the US and then came back to Australia, sat the airlaw exam and got an aussie ATPL.
Having heard a rumour that Virgin Airlines frowned upon people who went to the US and bypassed the Aussie system said pilot then went to sit the 7 aussie subjects - failed one and consequently had his aussie ATPL pulled until he passed all 7 exams!