Lastman: The 2005 homeowner guide states, not less than 1.2m and not more than 2.0m. Now that may have changed but I would assume the mimimum height is to keep out of reach of children and the maximum to ensure easy access in emergency and for servicing.
I don't know what that document is , or where they are getting the information from, and if they have references in it that refer back to the relevant NZ standard . I am guessing it is just a very basic non technical guide. But lines companies meterbox installation instructions for electricians I have seen, say the bottom of the box must be between 1.0 - 1.2 metres, which would contradict it.