The Medical Department holds a major exercise designed to test the system for getting food to hospitals and first aid stations in the event of an emergency.
It seems that the general plan is that food will be cooked at a 'supply centre' and sent out hot to each First Aid Post, although some places will cook their own food. The lorry delivering the food will be accompanied by a supervisor and two workers, and also carry two baskets of chopped firewood in case re-heating is needed.
My guess is that this is pretty much the scheme that was put into operation on December 8. It may or not be significant that one place we know the food supply arrangements never worked was the emergency facility at the Peninsula Hotel (Kowloon) which doesn't feature in the surviving record (papers belonging to Auxillary Nursing Service member Florence Robinson).
These papers show that regulations for the ANS made it clear that, whether in an exercise or an 'emergency', its members were only allowed to give first aid when specifically instructed to do so by the Medical Officer in charge of their station.
Source:
Hong Kong PRO, HKMS77-1 - 'St John's Ambulance Brigade Exercise...'