A program such as PvPgn could/will make it possible, all it will have to support is a home server, where people log in directly to your pc, that's where Hamachi could be useful, playing with friends on a private server, or even on the same network (don't need hamachi for that though) the idea seems quite simple when comparing it to WoW, in-fact I believe the login data to be very similar. Once the emulated files are out it will be easy, I think people are even working on it as we speak. I always played on B.net myself anyway and so did people on my network, so I don't really care that much.
The only thing that bothered me about B.net was not being able to play a game on B.net with others, along with someone on your own network. I think that has been remedied though.