There is no way the two would have worked together. Bane is all about control, and the Joker is the opposite. As I said before, if Bane knew about the Joker's existence he would have let him in Arkham. With all the criminals set loose, an atomic bomb threatening to destroy the city, the Joker would have a lot of means to have his own brand of fun, probably putting in danger Bane's plans for the city.
I believe if on the film the both would appear together it would be some sort of mash of this:
Ending with the Joker laughing like a maniac locked in his cell.