Hmm... Try this. Make a "cop" bank. If people get wanted and pick up the 3 wanted stars, then the money which they pay to pick up the stars gets transported to the "cop bank". Then the cops go to this "bank" (Should appear in the arpd HQ) and can collect the money there.
This is basicaly the same as bribing, just a whole lot more cumbersome and unrealistic. Also it makes it eaiser for one cop to "ninja" another cop's suspect = =.