50 minutes is going to be enough time in DTW. Worst case is that your Madison flight will actually land in B or C terminal, both of which are no more than a 10 minute walk through the terminal and an underground terminal with moving walkways to A Terminal. I bet that your A319 will be landing in A terminal, which is the same terminal that your Montreal flight will be leaving from, worst case here is that you need to get from Gate 1 to Gate 74, in which case I'd use the Air Train, hopefully your gates will be walking distance, but I would expect that you'd need more than 10 minutes for either scenario.

Sitting in CAE waiting to get on a plane to DTW right now.

PS: CAE is one of the smart airports that offers FREE WIRELESS! Great way to keep passengers happy.