Highway capacity actually declines when they are congested. ie, less vehicles are moved.
Buy the 407, make the 407 free to use, turn the 407 into a parking lot to mirror the 401, 407 may actually move fewer vehicles than it does currently--->407 users that pay extra to take a more circuitous route may be inclined to just use the 401 if it is more direct and no more congested. The people I know who carpool to afford the 407 tolls will likely not bother with carpooling if they are going to sit in traffic for free anyway.
I am baffled that people look at the traffic map above and think "we should make the 407 more like the 401" and not the reverse.