I think the OP poses a good question.
In my corner of the USA, we experienced the 2011 southwest blackout. My building has no generators. The streets were in pandemonium. Many people couldn't get gasoline in their cars to get to work.
I called my manager on a landline; he told me to come to work. I showed up. It was kind of a fun day at work.
Anyway, a few days later I asked a supervisor what the process would be like if we had a real state of emergency, like an earthquake or something. Do we still show up for work?
The answer I got was, if I remember right, something along the lines of "someone here at the building will call you and tell you not to come in".
It was probably a response the guy had come up with off the top of his head. Does anyone here really think they would call us and tell us not to come to work?
They can't even coordinate driver's helpers in a non state of emergency.
So I'll ask you, what would the process be like in a real state of emergency (earthquake, extra terrestrial planetary takeover, war, tornado, hurricane, tsunami)? When would it be reasonable for an employee to decide not to show up for work?