Good heavens.
The lay-off and recall procedures are clearly defined in the COS:CA/EA/CBAs.
These are legal in every jurisdiction where passed and supersede any guesswork. They follow the master common seniority list and that’s that.
Now there COULD be a scheme of early retirement or semi-paid leave negotiated and offered which makes less need for lay-off. But if and when they start there isn’t much question on what the contracts require to happen.