Hopefully this doesn't get lost in the multitude of threads about Prime... Anyway I was looking to see whether the state of MHEG-5 support on Windows had changed and came across this. It seems DVB Viewer developers are planning to add MHEG-5 support including for NZ but they need help. Specifically they need samples of our MHEG-5 so they can test it. You can see more details http://www.dvbviewer.info/forum/index.php?showtopic=35559 here.

I myself don't use DVB-Viewer and don't even use DVB-t so can't help but I'm sure someone here can :-) Do note that I don't think they require you to be a registered customer to help and they say they will release the interpreter under GPL so it may help projects other then DVB-Viewer (although I believe MHEG-5 is already partially supported under Linux specifically in MythTV at least although I recall there may have been some standalone app as well)