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