Is a Trans Tasman conversion possible and what's involved from someone who's done it?
If you are referring to doing an ATPL in NZ then converting back to CASA Im not too sure exactly on the process,
refer:
Civil Aviation Authority of New Zealand)
and
Civil Aviation Authority of New Zealand
However just to get the ATPL in NZ can be quite tricky (but not impossible)
You will need:
-a current CPL, Instrument rating, English proficiency test and Medical.
-7 exam syllabus passes,
-then find an aircraft suitable to the director to do an ATPL flight test in which, to my best knowledge outside of the airlines is a Mojave based in Wanganui, and pay for a CAA examiner to accompany you on said test.
Total cost=
Licence conversions (feel free to add that up)
exams 7 x 237.00NZD
CAA test and issue fee 2,759.00NZD
Aircraft Costs (how longs a piece of string)