JonathanB
I'd defy any controller worth their salt not to pass radar derived traffic info to an aircraft under a FIS (old money)/BS if they had identified that aircraft and they thought there was a chance of safety being compromised. It can even be given to aircraft not formally identified, but that the ATCO believes he/she knows with a high degree of confidence through other information sources is the aircraft in question (The phrase used being "Traffic believed to be you...").
In fact, the duty of care paragraph included in the new rules means that you could be found culpable if you just sit back and watch with the attitude of "I was only providing a BS".
The problem stemmed in part from the fact that pilots could not get it into their head that even under a FIS, they could be identified using radar for the benefit of the controller... it quite specifically stated that this did not imply that a radar service was being provided.
Simple stuff IMHO having flown professionally, and controlled.