Sure... what I meant to say is that they would not be allowed to make a radio call which revealed they can see where somebody is, using "radar".
They would have to be discreet in how they use it.
The sooner we have ADS-B the sooner this will be possible to do properly, and the regs on radar visibility by non authorised ATC/AFIS personnel will de facto fall by the wayside, which will be good for everybody.