Would it really be given to team B at the previous spot? The 2010 rules, which is the latest book I have for NFL, only lists two cases: spot of the kick inside B's 20, and outside B's 20. In the first case team B gets the ball at B-20, in the second at the spot of the kick. I don't see an exception for when the spot of the kick is in team A's end zone. This seems to me to say that it would be a touchdown for team B. Then again, the rule for a touchdown does not list this kind of a case...