SJ
This is what one of the manufacturers of a portable ADS-B In/Out device states:
Integrated GNSS SBAS Navigation. Utilizes TSO Certified uAvionix FYX GPS. Meets TSO-C199 Class B.
It appears to use “certified” and “TSO” in the same sentence and that chimes with my understanding.
An ADS-B In/Out ACAS would need to know where it is but ADS-B Out going to TCAS has no need to know the integrity of the GNSS resolved position. See ACAS Link "ACAS II works independently of the aircraft navigation,
flight management systems, and Air Traffic Control (ATC) ground systems. " and FAA piece above.
I’m not sure I understand you here. To push out ADS-B you must have a position information for the Extended Squitter (ES) of Mode S. For TCAS II I understand that this must be SIL=1 or greater or it will simply ignore it - however, SIL=3 is needed for full TCAS functionality. To be able to resolve the other position on a display then your TCAS II will need to know its position to provide Hybrid Surveillance warnings. The advantage of Hybrid Surveillance is that ADS-B detections do not require the 1030Mhz interrogations as the ES is being pushed constantly like a radio on 1090Mhz.
That is how I understand it, anyway!