Exactly - multicast is next to useless for this country's current ADSL infrastructure. The major bandwidth costs are the centrals and (I presume) the exchange backhaul... given the last IP hop en route to the end user is at the ISP, that is where the multicast benefit also ends!
5 users in the same exchange watching a 2Mb multicast vid will use 10Mb of central pipe and backhaul bandwidth between them.
In fact the only people it's really saving any money is the BBC themselves, on Internet transit costs (which given the low scale of the trials, was probably negligible anyway!)
The number of routers that had problems with multicast probably made it little worthwhile persevering with and so they appear to have put it on the back burner (indefinitely?) - there are probably hundreds of thousands of DG834s out there, none of them will do multicast.
It may benefit the likes of Be, as they obviously don't use the BT infrastructure, but given the rDNS of their interim hops gives no clue as to the actual whereabouts of the hops themselves, it's anybody's guess how they have their network set up!!
