https://gis.geek.nz/

Will need a login, may not be 100% accurate.

This site shows licence locations does not mean site is built

Local councils dont always get alerted for smaller sites until a couple of weeks before construction starts. 

You can only really rely on radio licenses in the RSM database or websites that map those licenses as a clue. They will usually be created about 6 months ahead of a site being built but just because a radio license exists doesnt mean the site will be built.