https://www.post-gazette.com/business/career-workplace/2019/...
I wonder what the restrictions were before. It specifically says emails were allowed. But I wonder if a person maintaining an intranet site could post a banner on it with the same message. I'm guessing not since it isn't designed for that type of communication. I'm not sure where the plugin would fall. Seems like the message didn't fit the intended plugin scope.
I would also guess the plugin only covers prohibited use and does not cover allowed uses (ie does the plugin say you have 1st ammendment rights when visiting Facebook?). I doubt the documentation states that the plugin shall provide users with their rights. It probably says something like the purpose is to provide users with policy or law information related to the site they are visiting so they don't break the law/policy.
The message merely stated that employees have the right to organize. Without additional context, I don't see how that is a concerted effort to improve the workplace. There would have to be a "unionize to improve health coverage, or wages, etc" type message. Otherwise, I could just stand at my desk all day and tell people as they walk by that they have the right to free speech, to own a gun, and protections from unreasonable searches, etc. It's not a concerted effort to make the workplace better, so it doesn't matter if I'm telling people about their rights (not to mention I would not be doing my job while on the clock).
Using a plugin to communicate that message is likely a subversion of it's intended purpose and would be inappropriate - similar to if she were maintaining the company intranet site and posted a banner with that information. They aren't mediums for individual communication (such as email or chat apps) but rather for company-to-employee messaging and for the sole use of the company. In this case, she misused company-to-employee infrastructure outside of its scope for her own communication purposes.
This is (a bit) like google buying property around polling stations and then preventing anyone from passing through to vote. They're not hurting google by passing through, but they keep shouting "get off my land!" Why would we let them weaponize property law to prevent others from enforcing their rights vis-a-vis google?
Your voting/property analogy is completely off-base. It completely ignores right of ways and public property. And if you have people actually trespassing on private property on the way to a polling place then they are in violation of the law and can be cited. I see no legal way that you can "weaponize" property law to prevent access to a polling location. Also, there's nothing stopping employees from exercising their right to concerted efforts off company time and property.
Nor use company resources/infrastructure to distribute it.