Most unions don’t allow managers to join, as they’re generally considered to be part of capital’s collective bargaining side, if not part of capital themselves. I think most modern labor theory includes a “professional-managerial class” to account for this.
There’s an argument to be had about where this line makes sense in modern megacorps but local managers in blue collar work tend to hold a lot of power over their employees in particular regardless of the shape of the corporation they’re under, so it would be surprising if they could.
Edit: fair points in the replies about management unions and that I was focused on a North American perspective. I was interpreting the post I replied to as saying the managers would join the union (as in the same one), but they didn't actually say that.
I can definitely believe that things would be different in a less union-adversarial environment. But it's still pretty unlikely that warehouse bosses at amazon would be welcome in the same union as the workers, or be likely to manage to unionize themselves successfully. The incentives just don't really align well in this context: corporate has too many carrots and sticks.
There’s an argument to be had about where this line makes sense in modern megacorps but local managers in blue collar work tend to hold a lot of power over their employees in particular regardless of the shape of the corporation they’re under, so it would be surprising if they could.
Edit: fair points in the replies about management unions and that I was focused on a North American perspective. I was interpreting the post I replied to as saying the managers would join the union (as in the same one), but they didn't actually say that.
I can definitely believe that things would be different in a less union-adversarial environment. But it's still pretty unlikely that warehouse bosses at amazon would be welcome in the same union as the workers, or be likely to manage to unionize themselves successfully. The incentives just don't really align well in this context: corporate has too many carrots and sticks.