Airbus ATC AUTO mode

[FlightDetent]

ACAS Guide Airborne Collision Avoidance Systems (incorporating TCAS II versions 7.0 & 7.1 and introduction to ACAS X)
May 2016

p.42 INTERFERENCE LIMITING
p.70 TCAS II/TRANSPONDER OPERATIONS ON THE GROUND

The techical explanation is not provided in that particular document, but guidelines are very clear.

--- edited ---
And a leaflet straight out of my flightbag, where a copy is stored for no apparent reason since 2004.

This brochure describes transponder operating procedures from departure gate to runway line-up, and landing to gate.

Full dedicated webiste here:
EUROCONTROL Documents on SSR Mode S | Eurocontrol