I'm not the legendary Masucci
, but I'll give it a shot...
Using NFHS rules:
The momentum exception is just that: an
exception. It applies
only when the rule that it is excepting would apply - in this case, 8-5-2a, which says that it is a safety if you carry the ball into your own end zone and it becomes dead there in your team's possession. However, that rule does not apply here because of 8-5-1:
Responsibility for forcing the ball from the field of play across a goal line is attributed to the player who carries, snaps, passes, fumbles, or kicks the ball, unless a new force is applied to a grounded backward pass, kick, or fumble. (emphasis mine)
Once the ball is back in the field of play, force is determined all over again - and the force is definitely the illegal bat in this play. So, 8-5-2a is no longer relevant (we'd use 8-5-3c instead), which means that the ME is off. And since the final result of the play is a touchback according to 8-5-3c, by 10-5-4d, the basic spot is the succeeding spot. 1/10 for R from the R35.
Under NCAA rules:
I believe the same argument can be made - the momentum exception applies to 8-5-1, which defines safety. But the rule to be applied is 8-6-1a, which defines touchback. 8-7-1 and 8-7-2b(1) help to clarify whose impetus (force) puts the ball in the end zone for the final time.
The catch is that NCAA rules have no equivalent to NFHS 10-5-4d. The closest they come is 10-2-2f(2), which requires the change of possession to occur in the end zone. Therefore, I believe the enforcement rule that applies is 10-2-2f(1), which says to enforce the penalty from the goal line. B will presumably decline this penalty and take the touchback, resulting in 1/10 for B from the B20.