Union elections are how that check is performed. Microsoft appears to be skipping this process though and voluntarily recognizing the union, presumably because

Union elections are how that check is performed. Microsoft appears to be skipping this process though and voluntarily recognizing the union, presumably because they know it would win such an election. This is probably only coming up because as a part of the acquisition process they are terminating and rehiring all the employees, which removes the existing union representation since the old employment relationship no longer exists. This is of course mostly just a paperwork exercise but is common in acquisitions since the acquired is not necessarily legally taking control of the acquired corporation itself, but rather its assets.