From the CASA web site
Renewal of ratings gained through the TTMRA process
Where a NZ pilot converts their NZ Instrument Rating through the TTMRA process, subsequent renewals of their Australian Instrument Rating must be completed within Australia, i.e. a renewal of an instrument rating outside Australia (i.e. in NZ) does NOT satisfy the requirement of a renewal of their Australian instrument rating. If the Australian instrument rating has expired for more than 12 months, the licence holder will be required to sit the IREX theory exam prior to the issue of the rating, as it will now be considered an initial issue.