He's on the roster, and he said he'd do whatever he could to help out the team.
If that means operating as an emergency quarterback, I'm sure he'd be fine with that. He knows he's not going to be the starter, unless something goes horribly wrong on the injury front.
Also, he has a real QB coach now, in the way of Gino Guidugli, who is a much better QB coach at ND than Tommy Rees ever had been.