All these "prison" servers are just improperly named in my opinion. I'd much rather call it "plot mining". That's what it is.
In all truth, every server and its mom is running an OP prison server or minigame nowadays. It's an extremely unoriginal idea, and Havocmc has very unique gamemodes. PvE The Walking Dead, PvP The Walking Dead, Hell Night, and Mine Wars are great examples of Havoc's standard (MW still needs work but it's pretty cool).
It's a nice idea but it's just so common and overused there's no point to it.