Could you please provide me some examples? I figure if California's prisons were 200% of capacity, there's no shortage of work for the prison guards anyway.
Much of the concept is that the prison's are at 200% capacity because of the perverse incentives for the state (prosecutors, police, judges) to fulfill the private contract minimums.
Mandatory minimums and the 3 strike rule are suspected to be related to private prisons contracts.
Then of course there could be plenty of hidden stuff like more prison crowds means some one selling food(I hear animals eat better food than inmates) to the prison likely makes more money, and hence better bribes/commissions in the chain of people involved.
Eventually it comes down to profit per person. And they'd like to make it up on scale.
I'm not sure how/why you figure that, or how it's at all relevant.
I'm not sure how/why you figure that because "over capacity" != "will build new prisons / hire new guards". I.e., it's not at all impossible for there to be prisons that are over-capacity and also a decline in the number of prison guard jobs.
It's not relevant because the entire point of unions is to counter-act the effect of supply/demand dynamics on labor (see: "there's always another scab"). Just because there's "no shortage of work for the prison guards" doesn't mean they will lobby against changes to laws that might one day create such a shortage.
I mean I get the initial point, some police unions are an especially vile proponents of an expansion into a police state, its just not really about working conditions. Its political lobbying. In Germany you can see it every time more competences for the police are discussed in parliament. You have some police unions giving legit feedback if someone bothers to ask them, how those competences are a bad idea and are not needed. And then you have speakers for other police union (with a catchy union name to seem more important) where you can see they have the right party membership and are looking for a career in politics. As a result you can see them in every news report that wants to bring across a certain message.