It appears it isn't prepared to give ground, no doubt encouraged by the plummet in the sharemarket price of Auckland airport shares. Given that Canadian Pension Plan only is seeking a minority shareholding anyway, you'd have to wonder how it would meet any of the xenophobic tests of "control". If the purchase does go through, then Dr Cullen will have only succeeded in one thing - decimating the price that Auckland airport shareholders could OTHERWISE get for their property. Canadian Pension Plan could always just offer less, given how Dr Cullen has just destroyed wealth.
Something governments are awfully good at.