See this cabinet paper (exec summary) from two weeks ago which suggests that both Telecom and Vodafone aren't fully using their 800/900 spectrum and so 7.5 MHz from each band would go up for auction when the licences come up for renewal.

I too read somewhere that Voda sold NZ Comms 6MHz last week, though haven't seen any details or confirmation. Perhaps they are trying to pre-empt losing it at the auction - get some money for it.

EDIT: in the recommendations section of the cabinet paper I see that if either Telecom or Vodafone sell at least 5 MHz on the open market then they get to keep the 7.5MHz that would otherwise be auctioned. So sell 5MHz now or lose 7.5MHz later.

Getting back to the thread topic, I wonder if this has something to do with TelstraClear shutting down its Tauranga network. Perhaps it will do a phoenix and will reappear using some of Telecom's 800MHz spectrum (and an agreement to roam onto the fabled Telecom WCDMA network - which I personally don't believe is in the works (yet)).