This is in Ontario Canada. This is most definitely not an "at-will" jurisdiction when it comes to employment.
The Ontario Labour Relations Act applies, along with common law. (The entitlements written down are not what applies -- it is what is "usual and customary" that applies in Ontario for severance compensation -- and that is *much* more generous than what is written in the legislation.)
Anyone subject to severance (of any kind) in Ontario should consult with a lawyer experienced with the practice of employment law in Ontario before signing anything.