There are apparently all sorts of procedures going on for what happens to your old license. I don't know about ON specifically but quite a few of my German coworkers in AB had exchanged their German licenses and each one of them had a different experience with the exchange, depending on where they'd gone. One guy was even given a license to drive motorcycles, trucks, you name it, by mistake. They were also told that AB would mail their licenses back to Germany where they would be able to collect them if they moved back but those who moved back found out that was not true. They were told that Manitoba sometimes mails licenses back but no other province does so apparently the AB government either keeps the licenses or destroys them.