AI Eyes and such would continue to work for the AI rather than you.
AI guard posts would shoot at the AI ships like they normally would shoot at yours, but otherwise would do nothing.
More than one command station would work, but would leave planet ownership on whichever one was built last, I think.
Spire city stuff I'm less sure about, but probably nothing.
So warp gates and reinforcement warp gate always give "warp covereage" to the AI, regardless of who owns the gate. Hmm.
So for the command station case, if would be in the ownership of whichever command station is processed last. (Generally build order, but things can get hairy if they were "
"built" at the same time, like in save game editing. As a user of an API (in this case the game program), I avoid making any sort of assumptions on processing order, as those tend to be messy details, implementation specific, and if I care about it, I'm doing it wrong)
One last thing. If an AI command station or the AI home command station somehow gets into human hands, would the normal command station build options be available to it, or would they provide planetary ownership and supply only and you cannot build using them?