I have a Retina Display MacBook Pro with the latest OSX and also installed Windows 8 RTM on BootCamp.
I hadn't logged into BootCamp in a few weeks, so I dont recall if the backlit keyboard ever worked on bootcamp or not. The thing is, I haven't been able to make it backlit.
I installed Power Plan Assistant (and Trackpad++), and the "Turn Off backlit keyboard" option doesnt do anything. I thought if I clicked on it, it'd toggle whatever setting it is it uses to actually turn it off, and I could use that to turn it on.
As far as I know, I have the latest bootcamp drivers (i update anytime I get an alert about that), and the latest windows drivers on the bootcamp install.
I've googled extensively about how to manually turn the backlit keyboard on on a bootcamp partition, but haven't find anything. I tried dimming the display to 0, then to the max, and that doesnt work.
If it helps at all, my function keys don't work either on bootcamp.