I was speaking to one of their staff over the phone about this, apparently they don't. They know if their product was different to the rest of the market there would be no point offering it. Vodafone is spending a shed load on the rollout. If you look at the incumbents like Sky, TalkTalk and BT, they all offer "totally unlimited" broadband....I haven't included Virgin as well they don't offer said feature.
Regards
John