I'm not sure on this, but you may have luck doing a wake-on-lan through a VPN connection. If you have a router running dd-wrt in the target location, it should at least be possible to talk to the router through VPN (which would be on all the time) and have it send a wake-on-lan.

My Power Mac G4 MDD would always wake up, every time, when I plugged in a certain transformer and if the wake-on-lan setting was enabled. I don't know what the deal was with that. It was very strange.