Hansen is in the watershed and will never be open to the public. You can fish the Upper Green River above it but don't go past the signs on the river. They get pretty nasty if you do. They worry about someone getting to that water supply and poisoning it.
Mud Mountain is great place to have a big picnic and it can handle quite a few. There is no reservoir there unless there is a flood so I doubt they will do much for public fishing. Not sure if they want a lot of hunters crawling around in there also.