Before Bertram is exonerated from the charge of being the mole he meets Lisbon in his office (without Jane, take note); look this images:
http://i48.tinypic.com/2a681va.jpg
http://i49.tinypic.com/2pu0k0i.jpg
http://i48.tinypic.com/1zezj8i.jpg
After Jane says that Bertram isn't involved with Red John. It's not a mole.
Timothy Carter must pretend to be him RJ. And he's believed RJ untile 4x01's end.
But there's a strange link to Bertram visible only after several visions of the episode:

http://i46.tinypic.com/2iaadlc.jpg

Why Carter reads (probably) a newspaper of previous day? The same of Bertram? Maybe in the news are writed the informations on Jane's family. And was made ​​to disappear and destroyed by Ron Deutsch, the security guard.
IN THE MENTALIST NOTHING IS PLACED AT RANDOM
When Gale Bertram says or does something suspicious, PJ is absent (poetry, tea, journal).

Following the logic: Bertram it's involved with RJ, in some way.
Is he a mole? I don't know. Is he Red John himself? Maybe. Certainly he's a strong suspect.