ATC Short term conflict Alert (STCA) is depending on ATS systems, there is no fixed parameter worldwide, but is typically 2 minutes, while ACAS audio warnings are dependent on altitude, but in the upper airspace , they start around 45 seconds before CPA. There are no coordination whatsoever between the 2 systems.
I'm aware that TCAS and ATC CA do not co-ordinate, wasn't my question sorry if it came off that way.
There has been numerous accounts however of TCAS going off and issuing an RA even when there's no airplane within 100 miles of their location.
Also TCAS going off and issuing an RA for "Traffic above" when tapes prove neither airplane infringed on the 1000' separation.
If TCAS/ACAS is giving RA's for airplanes that don't even exist, whos to say it will come up with the right answer every time when they do?
Obviously TCAS is an invaluable tool, and would have likely saved the Gol disaster had the Legacys transponder been on, but one has to wonder just how well it works.
It's not exactly easy to "test" it on a regular basis real world without endangering lives.