Just a thought, what kind of airspace was it where the situation occurred? I used to instruct in the US and as standard the Class D airspace around many relatively busy airports only stretched to a 4 nm radius, with Class E outside. The clever VFR pilot would stay away from the ILS corridor, but VFR traffic could operate legally without two way radio communication (and in some cases without transponder) just outside the Class D circle at any altitude from GND to 18 000 ft. It sounds in this case the controller was communicating to the aircraft involved, and just failed to give you proper information about it, but just thinking if airspace design could have anything to do with it? Also was the airfield radar equipped? Did the controller understand that the aircraft was straying onto the final approach path until you advised of the TCAS RA? You said the also the chatter was to coordinate IFR procedures.. therefore quite possibly legit? Not trying to play down the seriousness of the situation, just trying to elaborate on how a few unfortunate circumstances could lead to a good day becoming a bad day… quickly, as you experienced.