Sorry, I explained it a little better in the AMH thread.
Essentially during the "rise of the freaks", a man begins to parade as a fake Batman, he ultimately steps over the line and begins to even kill the cops who get in his way. Then its revealed he actually works for the mob in the end.
This is the source material Nolan has taken from, how true it remains, we will have to wait and see.
The appear in a complicated issue, at the end of issue # 1, Joker had accidentally stabbed himself. Now he is in the hospital, and this is really part of three stories in the issue. The fake Batman ultimately serves the purpose of throwing the police off while the mob comities crimes and cannibalizing Batman -- Go to the AMH thread, I put a lot of information about how he MIGHT fit into this and about the subject there.