Fumble into FOP
 

B9 intercepts A1 pass in the EZ and begins to run it out of the EZ before fumbling the ball into the FOP. A55 has a IBB during the play after the interception. A99 recovers the ball at the B-2. What is the call - touchback, safety, A ball.

Fumble into the EZ is one thing, going the opposite direction is a bit confusing at this time. Help me to understand - NCAA rules

Just for clarification for everyone involved. I am assuming you mean the IBB was before the fumble out of the EZ?

Peace

Fumble into FOP
 

That is correct.

My guess:

The team in final possession fouled before gaining possession for the last time. A’s ball after previous spot enforcement.

B got the ball with clean hands, so they will get to keep it. This is a foul by the team not in possession, so the penalty will be enforced from the basic spot for B9's run. The end of the run is the spot of the fumble in the end zone. When there is a change of possession in the end zone and the run ends in the end zone and the result of the play is not a touchback, the basic spot is the goal line. It will be B's ball, 1st and 10 at the B-10. 10-2-2-d-2-c.