Hi All.

Ok let me start by saying i work for the Hilton and at that hotel in particular
and ill just explain the situation. im a manager so at times i am in charge of the hotel and in such cases am in charge of the fire alarms.
if one of the sensors goes off a quiet alarm sounds to just staff in which case we go and check the area and the panel and are alerted if it is a real fire, if it is we go into full evacuation, if not we say false alarm and nobody gets woken up or anything. if its is checked and there is a fire, we press a big red button and whole hotel has to evacuate cause then the threat is real and even if it is secluded the law (and our common sense) tells us that this is a threat to our guests safety which is the the top priority at the hotel. however, if it is more than one sensor which is activated it means that the smoke/heat area is not contained which means that more than likely it is either a real fire which is spreading or that the area at risk is larger than just one sensor,
once the hotel is in full evac we HAVE to have fire men come and check it in case it is a invisible issue such as a electrical fault etc.
although fire alarms can be an inconvenience we never ever take them lightly, i would always rather evacuate the whole hotel for a false alarm than call of the fire brigade or treat an alarm lightly and have any one of my guests in danger.
that would have been the reason even though one fire engine turned up they still had to evacuate the whole building. it was just coincidence that it was 4am sharp.
i hope this clears up things a little more and also explains why the hotel system works as it does, the hotel never does anything to inconvenience the guest unless it is absolutely necessary
i hope that other than the VERY early wake up call the rest of your stay was satisfactory

Anna