I am not bothered about Ts & Cs. I can see that a network provider offering a large 'free' data bundle is not going to like tethering if some kid is downloading a few GB but that is not a normal person's usage pattern.
All that concerns me is whether it
actually works or not.
I have never seen any evidence that any network is looking at the data for indications of tethering. One insider told me that they might, in cases of heavy usage only. Any algorithm would throw up a lot of false positives because modern phones can run much the same apps as PCs, and if you run a VPN then nothing at all is going to be visible to the network.
From what I have found so far, the unlocked Iphone 4, with the latest IOS, does indeed support tethering via bluetooth. Whether the network likes it or not is not Apple's problem because they sold the phone SIM-free
