Notre Dame will "win" the Big Ten by virtue of beating Michigan, Michigan State, Purdue and Penn State.
I don't think Notre Dame's defense will allow them to win every game on that schedule. 3-1 is more probabe and anything like 2-2 is a disaster to be sure, but 4-0 is a lot to ask.
That said, unless they play Iowa or Ohio State, I don't think they would be beating the 2 best teams in the conference anyway.