What does the insurance policy itself say about pre-existing conditions?
This is not a matter of law, at least for the next six months; this is a matter of what the contract says.
Two things I am tired of typing: 1.) A wrongful termination does not mean that you were fired for something you didn't do; it means that you were fired for a reason prohibited by law. 2.) The above answer, whatever it is, assumes that no legally binding contract or CBA expressly says otherwise. If it does, the terms of the contract apply.