In I believe it was "First Steps" the one with Sandman, Hammerhead mentions how the Master Planner has put a charge on using the villains from the Six. He mentions it to Sandman when he talks about the oil: Bigman and the Planner are getting cuts of it, so it makes sense that Rhino would be working for Ock, but I don't know why these villains would let the Planner do that, even if he sprung them from jail!
So far 2 of the 6 are back behind bars. I'm not sure what happened to the Tinkerer (I would think he got arrested, but he wasn't with Beck last episode) so I'm not sure