Thanks, that's very helpful.
So I guess for Australian flyers who want to get a better deal with the NZD fares being somewhat cheaper, there probably isn't a way to get around that by flying to NZ and then starting the CP from there because once you factor in flights to/from NZ, it may end up more expensive.
Have to bite the bullet I guess!
The key fare rule for a xCIRnn to remember if wanting to commence in NZ (and being resident elsewhere) is this:
"When travel originates in a country for which a specific local currency fares is published and the
ticket is sold in another country, the fare will be that published for the country of origin converted to
the currency of the country of sale at the bank selling rate. The resultant fare must not be lower
than from the country of sale.
Exception: Not applicable for sales made and/or travel originating in Canada"
Effectively, if you live in, and purchase the ticket in, Australia, but for departure from NZ, you pay the ex-AU price (my contention is that as I rang the NZ number I was purchasing in NZ). This nearly got me (I knew the rule but believed it did not apply in my circumstance) last year when purchasing a DONE4 departing from AKL. Short story is I rang the AA NZ phone number (taxes and surcharges are significantly cheaper if purchased from AA) and the first agent decided as soon as he knew I was from Australia he was going to charge me ex-AU prices (I had booked the flights over the phone with the AA Around The World desk). I rang back a few days later and had it ticketed no problems (but there were some tense times in between). I think I was in the right as far as above rule goes.
So you probably need to have a Plan B, and allow for positioning flights, overnight hotel accommodation in AKL, and any credit card currency conversion fees you may incur. IMHO it is still likely to be worth it, but you need to check your own figures.