Even if the rule were found illegal, it wouldn't be illegal for any company to refuse access based on vaccination status, so no chance the company would be forced to pay a fine.
I'm not so certain that'd be legal. The idea maybe would have a footing if wanting to prevent those who are actually infectious, e.g. requiring proof of a negative COVID test, and because these vaccines don't prevent infection - and may actually lead to it being easier to catch [and therefore spread] COVID - it isn't akin to a negative COVID test result.
