For threading, I remember reading an article where the developers said it can utilize 8 cores.
I haven't really checked usage on my rig though for specific data as it really just runs smooth as butter and I just didn't care.
That being said, it seems like the game is much like BF 3's single player, and heavily GPU dependent, so I really doubt it's using 100% CPU utilization.
I can't really get back to the couple of spots where the framerate dropped though, so unfortunately I can't check to see if that was a CPU limitation or a GPU limitation. As I play, if I reach a spot that drops a bit, I'll go through it again to see what the issue is with the scene.
I really wouldn't worry about your CPU too much guys, I'm happy to repeat like a broken record that last light runs smooth as baby's ass.