Bill C-71, text of the bill.
http://www.parl.ca/Content/Bills/421...1_1/C-71_1.PDF
If you register it before June 30, 2018, you become grandfathered for prohibited 12(11), and can take it to a CFO approved shooting range. It's prohibited, so you'll need to comply with the prohibited storage regulations. It can only be sold to other people who own CZ858's and are 12(11) grandfathered. When you die it's destroyed. You can't use it as a non-restricted (e.g. crown land, hunting, etc).
If you fail to register it before June 30, 2018, there's a possession amnesty till 2021. However you must phone police to come and pick it up, and they'll take it and destroy it. If it's not registered, you can't take it to a CFO approved shooting range or anywhere else. It's a safe queen until it's destroyed.
If the bill fails to pass, then neither of these things happen.