If you are french working in a different country, you can contribute to the french pension plan through the "Caisse des Français de l´etranger" if you want to. However you would still have to pay the Canadian pension plan.

There is an agreement between France and several countries including Canada. Once you will retire, if you have worked 10 years in Canada and 30 years in France, then you will get 3/4 of your money from the French Pension plan, and 1/4 from the Canadian one.

This agreement works whether you are French or Canadian.