I've done 55 minute connections at MUC with plenty of time to spare (Int'l to Schengen even), but obviously that's MUC. Since it's going to be a D-I or I-I connection, it has a Min Connection Time of 45 minutes, so this is legal. Assuming he's arriving on a *A airline, departing on AC it should all be within Terminal 1, too. Depending on where he's arriving from he may not have to do immigration at FRA.

And of course since he's connecting to an Air Canada flight it's most likely his connection time won't be 45 minutes, but rather something on the order of 4h