I agree with "quiet investigations" being best.
Have spent a lot of years working radio in a different career field with maybe seventy (give or take) response agencies, multiple counties, and two states. Don't mind stating unequivocally that you learn who you're talking with during and after a call (landline/cell), who the newbies are coming up through the ranks, and so forth - over time. Until you get to know a name, voices and mannerisms become familiar, recognizable, and comfortable. I still occasionally listen to radio traffic on the scanner and generally know many of the voices after four years retirement.
Not suggesting an exact equivalence with ATC and the airlines but noting that voices and mannerisms of radio use are recognizable, especially if one would fly regularly through the same airspace and despite the large numbers of people doing so, given enough time. Would it hold up in a court of law? IDK. It might with the recordings certainly available; maybe it wouldn't.
Not trying to be adversarial but simply provide a different perspective.