For those of you with access to iOS 8.3 betas, check out your Siri Settings.
You can now set your Siri language to "English, New Zealand". The Australian text-to-speech is still used for Siri's voice, however it appears the input has been optimised for New Zealand English.
As an officially supported country, Siri now looks for businesses here. It will respond to questions like "where is the nearest petrol station".
Will be interesting to play some more with this and see just how good Apple's data is.