What you've said about BT's method is basically correct.
Really all I'm saying is that you will see the effects of contention far sooner than BT's customers will. It is generally accepted that BT's current 50:1 contention ratio will be unworkable when the number of customers and bandwidth usage grows.
You might find this interesting:
http://bbs.adslguide.org.uk/showthreaded.p...essbb&Number=934842Personally speaking, unless you want to P2P with you neighbour, bandwidth "inside the mesh" isn't going to be a lot of use.