Sounds like it’s time for a folder.

Or to check if that original all-hands teams call was recorded.

Then what? Okay you can prove them liars, but that won't surprise anybody and won't change anything in the course of the company. I don't even mention the likely personal repercussions from speaking truth to power: "not being a team player" and and and.

If one is already being fired or forced out due to broken promises, depending on their personal circumstances and how well documented such broken promises are it could be worthwhile suing them for it.

You are quite correct that continuing on with the company (or in that corner of the industry) may - well, likely will be - impossible afterwards. Few things say 'burnt bridges' like a lawsuit. That said, being fired because of a promise they broke is them starting the bridge on fire anyway.

Either way, the CYA handbook is - document, document, document. And keep it where no one but you has control over it. You have no power if you can't prove anything. And documents 'go missing' or get 'automatically removed' from company equipment all the time in situations like this.

knowing if you even have a case or complaint is also important - which is only going to be possible if you can see what was actually said (not what you remember being said) or written. Sometimes we hear what we want to hear, not what was said. Knowing that BEFORE you show up in court is rather important.

As I wondered in some other place: do you consider a promise made in a newsletter or an all-hands meeting a binding contract? Would a court consider it binding, or rather an information about the current course of the company? And changing that policy in the subsequent newsletter or all-hands, wouldn't nullify anyway whatever binding value the previous one had? (I'm not talking about employment contract changes, yes those are binding)

That would depend on the specifics. You’d want to discuss it with an attorney.