SteveON: IMHO NZ doesn't need these - we have low density populations and an abundance of spectrum.
Spectrum isn't the issue. It's the fact that in certain situations it's virtually impossible to engineer a mobile network that will cope.
Basic physics imposes a RF noise floor - that's not something that can be overcome.
Even with all the gear in the stadium in Wellington it suffered a complete mobile meltdown during the recent All Blacks game for both Vodafone and Telecom with 2degrees being badly impacted. While thing have been badly affected in the past, the growing increase of data puts a lot more load on networks than voice traffic. In the TDMA days engineering was also a lot simpler - you either had a voice channel or you didn't and got a busy tone. Modern CDMA based air interfaces are very different.