Not sure who told you that. Most employees with either have options (which can become shares, but aren't) or Restricted Stock Units (RSU's) which are useless till vested.

Either way their holding will be miniscule, even in aggregate, compared to other shareholders. Even if it wasn't miniscule, they would still need to organise, maybe form some sort of coalition, or "union", in order to leverage their collective voting power against other large, unified, shareholders.

Google gives out Class C stock options to (most) employees, so even when they vest they can't vote. They're certainly not alone in that. So, no, probably not?

Even were they, the voting capability of such a share is ineffectually small; this is the "why you can just not spend money at MegaMart if you care so much" [because singular action doesn't work but we can make it sound just viable enough that you go away] argument tilted a little.

The total percentage of actual vested shares that are held by the rank-and-file workers is minuscule at best.

That sounds more like a cooperative. Outside those situations stock ownership means very little for rank and file employees.

Especially with the multi class share structure with different voting rights.

And talking of employees shares lobbying for changes to the taxation of those to make it fairer would be an good thing for unions to lobby for