Does the firewire hub on the Apple Cinema Display's provide bus power ?

That's actually a pretty good question. I've never hooked a bus-powered device to mine, but I'm nearly certain it does--otherwise the connector would be the mini powerless kind, I'd think.

Now, whether it's supplying the 12V or just passing it through from the computer, I don't know, though I'd suspect it doesn't supply the power itself. It'd be easy to check if you had a bus-powered device, though; just unplug the FW cable from the computer, hook it to the monitor, and see if it powers up.

No, you can't

Sorry for necrobump but I came across this thread a few weeks ago.

The answer is a resounding no. However, you can feed 12V into the firewire cable from a seperate adapter (I wired an old portable HD cable into a female firewire port) , and tap into /that/ 12V on the cinema display.

I'm powering an led strip from it.