Actually, I think you will find that Hamilton didnt work for Air NZ because (1) Air NZ have a poor presence in the Australian market, (2) Hamilton is not a well established destination in Australia and (3) Air NZ prices were too high for the Hamilton market. Hamilton had the outbound numbers but inbound numbers were bad as a combined result the above.
Pacific Blue will do much better because there is price parity with Auckland, Pacific Blue has a well established brand in Australia, and Waikato Tourism is getting a good kick in the behind resulting in better awareness in the Australian market.
Hamilton didnt get the international numbers with Air NZ because an hour down the road (at Auckland) were much cheaper flights to the same destination. De Ja Vu if you ask me for Rotorua - because now, just an hour up the road from them is Hamilton with cheaper flights to the same destination.
Also - Sydney is a real dog of a market at the moment - recent publications show that most airports are suffering on that destination at the moment. Pacific Blue booking slowing is not surprising because most airlines to Sydney will also be experiencing similar reductions in bookings.