Atleast where I live, when you fire someone that's it. They're fired. Even if they still work for 60 days because that's the minimum notice period. The only way to reinstitute the contract is if both sides sign a new contract to overwrite the termination. And this can be used to amend the employment contract too.

So where I live, you'd be in a prime position to negotiate better paychecks because without both employee and employer agreeing, a termination has finality.

iiuc the California WARN act doesn't let a large company (more than 15 employees) just fire half the workforce, so I guess these people have been locked out of their work accounts with full pay and informed of a future termination date.