you are correct SeeMyToe that there have been a number of these incidents over the years and the travelling public never gets to know about it. Many are not aware that CAD management has ruled this procedure to be the normal despite it being illegal under ICAO requirements.
There was an incident in non vfr conditions some years ago where a helicopter with transponder off was crossing the runway at the wrong end as a 747 rotated. A close near miss eventuated and still the procedure remained in place with no reports filed outside CAD. The time is long overdue for a completely independent Air Safety Department to investigate incidents and forward conclusions and recommendations directly to the Transport Minister and by pass CAD altogether.
if there is a collision one day and a helicopter with transponder turned off is a contributing factor, CAD management over the last 5 years will not be saved from jail time. The Hong Kong Government may also be liable for massive compensation payments when the insurance companies refuse claims due to an illegal helicopter transponder procedure.