ATM over ADSL
Impossible. Can't be done. Definitely not what Homechoice used to use to deliver broadband video to the home in parts of the South East UK, long before the IPTV dreamers started slobbering over the "quad play" opportunities and calling Homechoice IPtv because they struggle to find a *real* IPtv success story so far. PPPoA? Completely different.
How would the T-Mobile 3G<>DSL model work in the UK? Upstream bandwidth wouldn't be much to write home about, and downstream would be a bit ropey if more than a couple of folks wanted to use a cell at the same time, especially if the transmitter was any distance from the exchange so the DSL sync speed was lowish. And when you're close to the exchange, the obvious place to put a base station is the exchange's very own roof, which already has power, all the fibre bandwidth you're willing to pay BT for, and planning permission. OK there are only a few thousand exchanges and 3G needs rather more base stations than that, so maybe there might be some mileage in this T-Mobile idea, especially in the areas fortunate enough to have LLU DSL coverage (which are probably also areas with 3G coverage).
But it may not bear thinking about for anyone who might be relying on using their 3G phone as back up to their DSL broadband ;)