CPs can't migrate to WBC until the exchange has 21CN available
It's germane for people like me, who until now have had no ADSL2+ options other than the two LLU providers in the exchange (and their wholesale partners). Which eliminates most of the interesting offers that pop up from time to time, such as the current one from Plusnet Business.
3 km line on THTG: 19/1.2 Mb/s with Sky
Previously: BT ISDN, Nildram, Plusnet, 186k, EFH, Be*, Plusnet (again), Pulse8