Had a statement from freeview that TVNZ have made some major changes this week including

1. Slight delay between the regional TV One feeds
2. Statmux software upgrade

Whils there might not be much of an average bitrate change, the system should be able to peak a bit better when required for higher motion scenes.

I can't comment on this yet myself as I'm away in OZ this week, but I'll take a look at my recordings when I get back.