Union vs union happens all the time on the worksite. Try changing lightbulbs at a factory without being part of the electricians union
Unions really don't have much to do with this problem. It's merely an aspect of the division of labor. It's also probably a net-negative for the factor to have production stop so a worker can replace a bulb (assuming the production isn't stopped because of the bulb).
If you went in and made unauthorized changes, for sure.
> Do they demand to be paid wages lost from your usurpation of their role?
That depends. If we're talking about, say, government contracting, and the LDAP team is paid on a per-request basis, and you circumvent this, yes, they would rightfully demand to be paid what they're entitled to in the contract. Of course, in this case, it's probably two separate employers in one larger organization, but it does happen.
In the case of unions, the union has a contract to do certain things in return for certain compensation. A condition for doing it at a certain price might be that the contract is exclusive. Plenty of examples of this type of pricing in the business world.
So, not really a unique union problem.
At public companies in the US, people get paid to review your LDAP group membership requests for a simple reason: CEOs and CFOs don't want to go to jail for failing to comply with Sarbanes-Oxley.
If you're at a private company, though, and you think the change controls at your company are a net loss in value, that seems like something to discuss with your CTO.