I don't know about NZ, but in many parts of the world you'll find plenty of illegal operation both above and below the standard 26.96 - 27.41MHz band.
Reception varies tremendously by conditions and frequency in use. During the last high sunspot period I could regularly hear American CB operators from the deep South. Some were running a little more than the legal 4W of AM, but many were just regular legal sets. The 10-meter amateur band being so close also behaves similarly.
