Two different sources have stated that NetCom would launch tethering support as of yesterday (to coincide with the iPhone 3GS launch). I can't see anything on the NetCom site itself though.
I can only say that there is no sign of it yet on my handset (but then mine took three days longer than expected to receive the visual voice mail update - no idea why) - so keeping fingers crossed that its on its way.
Update: 18:55 4th august 2009.
Regards the network update mentioned in the comments.
MMS: Yes Tethinging USB: Yes Tethering Bluetooth: Yes
So - thanks to NetCom for enabling the service ;)
Note - if you've hacked your phone to enable this before - you'll need to make sure all profiles etc are removed or it probably won't work.
For my part - I'm glad to be able to use the service without hacks. As mentioned in the original post - I was happy to test but didn't want to run with hacks enabled.