^Yes, of course CTU always has a mole.
The problem is that evil psychopath Dana from later in the season would have executed her ex-boyfriend and his mate without a second thought. She wouldn't have dragged Cole in to it, she would have just set them up to meet her somewhere and put one in the head and one in the chest.
She wouldn't have left a scrap of evidence and there would have been nothing for their parole officer to go on.
Frightened victim Dana from earlier on in the season couldn't possibly have been the mole.