Dang. I don't think it's coming from that area over the attic. I poked my head through the access panel in the garage, easily 12-14 feet off the ground. I didn't have the guts to lift myself up into the area, but I was able to look around pretty well and there wasn't a single thing in that space that would have electrical power running to it.

The mystery continues! Sometime I'll have to try to get back into the attic space over the bath. It's a very difficult area to get to...