Hiring the P.I was complete genius on RJ's part. I can't be the only one who thinks she looked a lot like Summer, coincidence? I think not, which means that RJ would have to be somebody who knew about Cho and Summer. Also, whether they caught the bug or not RJ would be in a superior position to either lead Jane into a trap or have the CBI office bugged. Correct me if I'm wrong but didn't Haffner still work for CBI during that time?
Haffner also fits all of the descriptions we have on RJ thus far, he is my number one pick for being RJ.