Vaananen Pasi NTC/Boston said once upon a time:
Basic idea is that the telco has xDSL links to subscribers and you are
supposed to run ATM over that link. So the access network is "simple
ATM network", with VP (or VC) connections from individual subscribers to
your favorite ISP's or company network. PPP / L2TP over the ATM are the
protocols of choice to run on top of ATM.
US West is planning on handling all the ATM internally, and dropping
ethernet on both the client or server sides of the connection. Everything
shows up on either side as layer 2.