I switched through to TVNZ to see their new HD shows.  TV One lit up the AC3 light on my surround amplifier, but as you have already noted I think it was just broadcasting 2 channel.  TV 2 did not.  

Bourne Identity was positively criminal not to broadcast HD with 5.1. Why would they not do this!  It doesn't make sense.

TV Three show the HD logo only after the adverts at the start of each show sequence, I must admit I dont like the TV logos on the screen all the time but if we must have them then adding useful info like HD and DD5.1 would be great.  TV One obviously only do this for Freeview so I assume this info is added at the transmitter?

The MHEG EPG tells you which shows are in HD and also if it carries a dolby digital sound stream.  Its a bit of a pain searching through it for this data, I hope that the Herald listings start showing this, or maybe that cool application from Orsome for the iPhone and iTouch could have it.