For me i can see the reasoning behind a 2nd Auckland side, going off population if you were to add both Christchurch and Wellington regional areas it would be around just over 1mil, which if you add the population regions in and around Auckland and BoP gets around 2.5 million, yes the warriors are already in Auckland, but that is half the problem, do you want a cross town rivalry in a city that follows RL, or do you want a cross region rivalry in a not so RL region and then they are split over 2 islands effectively splitting that demographic into Wellington being really not so hard core sport, and Christchurch being hardcore union?
Personally i'd say go for the Wellington/LowerHutt -Christchurch area anyway and try it out (but i'm a tree hugging expansionist)... and if they still want to throw in another nz based team you can in splitting Auckland at anytime.... but it looks like they'll do that straight away