I just returned from French Polynesia flying MEL-AKL-PPT vv. on NZ, so can provide some interesting 1st-hand experience:
MEL-AKL - no problem accessing the NZ lounge at MEL, due to the trans-tasman flight
AKL-PPT - showing up at the front desk at the AKL lounge, presenting boarding pass and Velocity Gold card (did't have the status in the booking as I was on a LH redemption ticket), the lady said she wasn't sure about access "as it only applies to trans-tasman" (her words); I then pointed out that we have just travelled trans-tasman as part of the same booking, coming from MEL, so I understand we would still qualify (I was unsure but simply tried that argument); the lady was still unsure but did let us in, we were lucky; I wouldn't have complained if she had turned us away though.
PPT-AKL - I knew that there is no lounge access for Velocity Gold at PPT nor any other benefits due to the Pacific Islands rule, so I didn't bother about status at all when checking in.
Then something interesting happened: we had 1 piece of luggage to much (3 in total, with 2 travellers on the 1 pce rule). The friendly and very helpful Air Tahiti agent asked if I would have "any frequent flyer status with Star Alliance or any other NZ partner", so I said yes and gave him my Velocity Gold card. He had definetly never seen a Velocity card before nor heard of the NZ/VA alliance, and also couldn't find any reference in his paperworks. So he apologised and went to see his supervisor. After 3 mins he returned smiling, "Okay, all problems solved!". Additional luggage: no problem. All luggage tagged as "Priority" (it came last off the belt at MEL but that's someone else's fault), and also got an invitation for the lounge (which was especially nice due to the 50 min delay). I am pretty sure this is not the rule but founded on the limited knowledge about the NZ/VA alliance esp. at out-stations, which can work out either way.
AKL-MEL - due to a delayed arrival and short connection we didn't go to the NZ lounge but straight to the gate, but I am sure as the upcoming flight was trans-tasman, access wouldn't have been a problem.
Two more observations:
Papeete is named as one of the "Pacific Island" services in the fineprint of the VA/NZ alliance, but NZ actually seperates PPT from their other Pacific Island flights and considers it as long-haul (just as PER is not trans-tasman but long-haul). So you get free f&b and also luggage rules are different. Odd that they nonetheless put it in the same basket as RAR, NAN etc. for the VA alliance then.
Also, according to the website you should get priority boarding as a Velocity Gold and Platinum for trans-tasman flights on NZ. However, there was no mention of Velocity status pax, only the usual NZ and Star Alliance status pax were called, at both MEL and AKL.
And apologies for writing a novel.
