TCAS should not generate any RAs when the carrier aircraft is below 900 ft agl only TRAFFIC advisories. Our flight test department specifically does not do TCAS ramp tests because it could generate false alerts.
There are several freighters that are routinely parked alongside the main runway here and they have generated alerts - probably because the baro pressure has changed since they shut down and their Transponders are still live.
BTW for certification tests, a ground-based transponder with a variable altitude input (known as a parrot) is set to (say) 1200 feet agl. The aircraft under test is then flown at above and below that altitude and the crew ensure that the correct RAs are displayed & announced.