It depends on the specific technology. VDSL and VDSL2 (which are unexciting in that they use EFM instead of ATM, and so they're basically literally ethernet bridging technologies) have modes (and i think it might be related to specific chipsets, it's not something I've been able to get working with, say, the ActionTec C1000A you can buy at Best Buy) for peer to peer mode, which sort of replaces some of the older symmetrical DSL standards that themselves got used as T1 replacements. (SDSL and g.shdsl.bis in particular.)