Right Way Up:
If you ever have spare time in an airbus sim try climbing from optimum to somewhere near max alt with blocked pitots. The flight control laws lead to pretty interesting results!!
Are you referring to the Vmo/Mmo protections, or something else??
This is a bit different than a conventional bellows/aneroid type airspeed indicator. The pressure would still be trapped (unchanging) between the pitot blockage and its associated pressure sensor, but the static pressure sensors would be dropping together and would likely pass validation. If the system merely calculates delta P to get the airspeed, then the airspeed would wind upwards pretty evenly between the 3 ADR systems. Normally the pitot side pressure would be dropping if you climb at constant IAS, but would be matched by an equivalent static pressure drop.
The constant pitot pressure, dropping static pressure situation resembles an acceleration and should be amenable to some sort of validity check, because in real life it would be hard to accelerate as you climb, particularly at altitude. At some point, you exceed the aircraft's performance capability.