I am not sure with the new pilot agreement (cost savings) that BF areas are reserved for crew rest any longer. In know on the 757 service from CLE to LGW, it used to be 1B was reserved crew rest (pilot), but is not any longer. In fact on my return on Sunday the BF cabine was full.

I have found that while those seats are blocked they will eventually open up. Some people don't like the back cabine, but the service can be better and usually is wrapped-up quicker which means better for sleeping...