If you have 1200hrs co-pilot time, you can only count 600 hours towards the ATPL total time requirement. and You will also need 250pic as well (100hours could be from the copilot time)
300 + (2400/2) = 1500 ATPL total time but 2700 total time.
You can use your ride/type rating/ppc for the ATPL flight test requirement if it's done by Canadian examiner.
And make sure you get your ICAO ride done for the company you work for. If you do this on your own, you will have to write INRAT again, if your Canadian IFR expired more than 2 years.