First see the end of this video: http://www.youtube.com/watch?v=pyhCIR4e4MQ
We see Bertram talk with Lisbon and after she leaves we find out that Kirkland was behind the door listeing. When I first saw this I thoght that none of the two were Red John and that they were working together to find or to help Red John. But with what we know right now I see this in a different way. 
If that guy is Bob Kirkland and if he didn't lie to Jane in 6x04, that scene doesn't make sense for me because we know that Bob was working to put the Tiger Tiger organization down, he doesn't trust policeman specially high up, so why work this close with Bertram??
One possible look at this is that, Bertram is Red John and that guy is the other Kirkland brother, RJ friend. 
Yeah, I don't like this theory because it envolves twins and stuff and I always feel like that is a soap opera kind of material but never the less is a possibility.

PS: Bruno Heller let Red John be anyone except for Reed Smith (and Bret Stiles). I kind of both love and hate this show right now :s