Qantas NZ were leasing the jets from AirNZ/Ansett anyway - I think this was a hangover from when News International owned 50% of Ansett New Zealand, and may have leased them from Ansett Australia, which was then bought by Air NZ.

What I'm getting at is that AirNZ may have had no choice about taking over the planes - Qantas NZ reneged on the lease, so they're stuck with them, unless they can get out of the deal with whoever they leased them from?