Just used it this morning (A319, RVR 125).
I called out "ALERT HEIGHT" at 100 ft RA
Captain checked that everything worked fine and called out "CONTINUE"
Uneventful autoland ensued.
In practice during CAT III DUAL NO DH approach, before Alert height, we would have gone around for folowing indications
-alpha floor activation
-AP off
-loss of CAT III dual
-amber caution
-engine failure
-no LAND mode at 350 ft
- incorrectly displayed loc course at 350 ft
- NWS or antiskid failed
Below alert height we'd go around only in the case of autoland warning light. It goes off if both autopilots have failed, excessive deviations or loss of loc / G/S signal is detected or difference greater than 15 feet between radalts exists.