On the first page of Blackest Night #1, when Black Hand is digging up Bruce's body, he says, "Some things are worse than death. Some things..like me. My father said, "Everyone dies, William." He said, "Death is the only thing you can count on in this universe." I killed him to prove his point. Death compels us because powerful or weak, loved or hated, noone escapes death. That includes you. The dead will rise. And you are connected to them all." Then he licks Bruce's skull.
If you remember a story in the JLA series called Tower of Babel, everything Bruce had on the other members of the JLA was used against them by Prometheus. He took out almost every member of the team. Bruce knew anything and everything there was to know about the DCU...who was friends with whom, lovers with whom, who were enemies, etc. etc. So, it would make sense that, assuming that it is in fact his power battery, Black Hand would use the skull of the man who had every bit of information one could possibly imagine about the DCU. If that's his power battery, I'm assuming everything in Bruce's mind is accessible to him.
Of course, there's also some dialogue that suggests the skull is talking back to him while he's giving the speech, and I have a pet theory that when Scar says, in Green Lantern #44, "The Black Lanterns are collecting hearts full of the splintered light, and soon it will be his turn to rise.", he's referring to Bruce Wayne. It just seems so far out there and unbelievable that I would not be surprised at all if, after getting trapped in the Omega Sanction and whatever the hell it was that happened at the end of Final Crisis, something happened to Bruce and he is the one behind the Black Lanterns. Maybe he instructed Black Hand to find his corpse and use the skull as his power battery, and once it hits 100%, he'll reanimate or something. I don't know, it's too early to come up with anything beyond that. Maybe the reason Thomas and Martha weren't raised is because he forbade it. Everyone else is fair game.
That's just my pet theory, though. I think it would be friggin' awesome though.
Of course, my other theory is that, like Mike just said, his spirit is separate from his body and he'll be leading the souls of those who have been reanimated against whatever force it is behind the Lanterns.