I work C terminal airspace in Oz. If we are using ATC or pilot visual sep we are required to tell relevant IFR a/c "TCAS traffic ... (bearing, distance)... maintaining visual separation" so they know what's going on in the event of a TA.
Additionally, if the guy on visual sep will have less than standard wake turbulence separation we have to give a "Caution, wake turbulence". It seems to work a treat - everyone knows what's happening.
AA