Really?, are you saying Mode S will initiate a TCAS advisory?
Yes - 37 years and 25,000 hrs flying Boeing 747 etc. TCAS was developed before ADSB was even thought of hence it uses transponders Mode A C or S.
There are no - repeat no - transport jets that only use ADSB in...........
I believe TCAS is based on ADS-B but requires a certified GPS
Sorry totally wrong.
The confusion is based on misunderstanding how all this airborne equipment works. The various jets I flew were gradually fitted with ADSB-out in response to ATC improvements under FANS. Areas such as the Pacific and Northern Canada now use ADSB signals for ATC as there is no possibilty of conventional radar in such remote locations. This was in addition to the already fitted TCAS and transponders and makes no difference to that.
The next development is ADSB-in to allow the display of target labels of proximate traffic with a view to "climb in trail" etc ATC functions. Non of the 777 and 747 aircraft in the airline were fitted with this and still aren't.
Some airliners do have it but not as a standalone replacement of existing TCAS/transponders thus all light aircraft with any transponder will be seen and acted upon.
The SIL=0 is of purely academic interest unless you are using a simple ADSB transmitter with no transponder and getting close to the big jets.........