There are models in Europe, where the government regulated that the last mile be open access that many companies can have access to. There are different ways of implementing that. Britain split British Telecommunications into two, a network--basically a Bell Nexxia--and a Bell retail, so that they don't have a conflict of interest. Other countries have used regulation without splitting the companies.
In terms of the billing, it has to be bulk, because an ISP buys in bulk.
All of the Internet works on a capacity basis. There's no point in going to UBB at one point. This is something that is done at the retail level, and it should be under the full control of the retail ISP, not the wholesale provider.