I heard something similar to this last year on the Syracuse, NY, feed.
There was a C172 just north of the airport with a CFI and student aboard practicing some maneuvers while ATC was vectoring a Dash-8 (60 seat or so high-wing prop aircraft acting as a regional carrier for USAirways) nearby for approach.
Despite being VFR, the C172 was given the restriction of 2,000 feet and below to which the CFI acknowledged. The controller then pointed out the traffic to the Dash-8. A few seconds later the Dash-8 pilot called traffic in sight and then the controller responded with, "Maintain visual separation with the C172, cleared for the ILS 28 approach."
Perhaps a minute passed when all of a sudden the irate pilot of the Dash-8 calls approach to let them know they were responding to an RA from their TCAS. The pilot then attempts to blame the C172 pilot for "getting too close to their aircraft" and the pilot goes on to berate the controller. The controller calmly responded with the fact that the C172 was maintaining 2,000 feet and below and had not gone any higher during the incident.
"WTF, Dash-8 pilots??" I was thinking as I heard this on the frequency. Didn't you just call traffic in sight minutes earlier and acknowledge the instruction to maintain visual separation?
My guess as to what really happened? Both pilots of the Dash-8 went back to eyeballs inside the cockpit after acknowledging the visual separation while they briefed and prepped the approach and were jarred back into reality when their TCAS screamed.
I should have made a clip of that exchange for here, but at the time I didn't think of it.