EDIT: I tried it just now since I don't give a f*ck about CoD, it seems like it works just fine. I think CoD sort-of stores your profile between systems online so it doesn't matter what you do on each platform as it's a universal profile/stats. It simply downloads it to either console whenever you play. That's really what BF4 should have done, they simply "freeze" your account on 360 although you can still get Achievements & such.