First observation there are no c/b's on a 346 flight deck. Only resets. To silence the horn the c/b is in th e/e bay. Dont think someone is going to climb down the hatch during a ground run !!! Only thought is if they pulled both LGCIU resets ?? Have to look at the schematics to see what that would do. Having said that you would probably have c/b pulled as part of checklist for high power runs as on most other airbuses and boeings . Be interesting to know the REAL story , if it ever comes out.