but it made me wonder if those of you working ATSOCAS routinely coordinate against aircraft on a Traffic Service without advising the pilot of the coordination.
Bookworm,
As someone who works ATSOCAS regularly, I will often coordinate aircraft working under a TS on my frequency against other Deconfliction Service traffic without immediately telling the pilot. However, I will always tell the pilot about the coordinated traffic when the aircraft in question is between 5 and 10 miles away.
If it is quiet enugh to do so (and this may not always be apparrent on the frequency), then I'll do my best to inform the TS pilot nice and early to ensure that they are aware of the coordination in plenty of time. The last thing I want is the DS aircraft still descending 2000' above a coordinated TS aircraft, and the TS aircraft getting concerned on TCAS and taking avoiding action of their own.
Hope this helps
Dave