Updated response from Sky/Prime:

Prime's listings are not available on TiVo's EPG (electronic programming guide) as at this time TiVo does not measure ratings data. This information is important for a free-to-air broadcaster as we need these ratings to put a value on PRIME's TV commercials.

We expect that this feature could be available in 2012 when we will review this decision at that time.
This seems to me to be an invalid response, since I don't see how Prime would get ratings data if I use a standard Freeview decoder or a TiVo. It makes no difference as they still have no way to tell what I'm watching. Secondly, this did not seem to be an issue to TVNZ and they also broadcast commercials.

In my opinion, this is not a valid reason but merely an excuse for anti-competitive behaviour as they try to prevent TiVo from competing with MySkyHD - and it will backfire as it net result will be that TiVo viewers simply stop watching Prime.

I feel that TiVo users should make as much noise as possible to Sky, and consumers shows like Target and FairGo, so have this brought to light and fixed in less than the 3 years Sky are proposing.