New Zealand has a reasonable inventory of spectrum available for last mile solutions due to its population density, so saying whitespace will fix rural broadband with a magic wand. Power, backhaul and network management need to be provided, usually on commercial terms which any provider will need to cover. Quality of service will also come into it. If you have a shared (spectrum) space, how does it impact on the end user experience?
Note any statement I make on whitespace is my own opinion and not of my employer