NTL have just given its broadband cable customers in Manchester public IP addresses to replace their private IP addresses. NTL state that this is to get around P2P and multi-player gaming problems.
This may be the whole reason, or it may be a counter attack on BT. One of the big sales area for ADSL for BT is businesses, which isn’t an area the cable companies have been aiming at up to now. Giving people public IP addresses could be a move towards this, as it will make it easier to run a server on their cable connection.