You can keep the same Apple ID. Only the country changes. The iCloud Music Library also stays the same., including the Photo Library.
I recently made the change from US to the Indian store. When I contacted the Apple reps regarding the process, they asked me to download and keep a copy of all my apps, movies and music as they may be lost once the transition takes place.
Even if you have not downloaded the apps, do not worry. As long as the apps you want are available from the Canadian app store, you can download them without having to buy them again. Just a heads up though, while trying to download an app already purchased, say iMovie, the App Store will show the full price of the app. You have to follow the usual process associated with purchasing any app but just at the last step you'll get a pop up saying that 'Update is free as you already own this app.
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Hope this helps. Had a tough time myself when I was planning a change.