The way I read the criteria on Emergency Services is that every day there is likely to be a large percentage of people there not in an emergency (routine precedures, visiting etc) so if a nomination is not near the Emergency Entrance I would consider accepting. (I have refused plaques etc as they where close to where the ambulances park).
In regards to Fire Stations locally they will occasionally have open days etc but for the majority it will be all used for emergencies.
If I was to review yours, unless I knew the Station myself I would only have your word that the nomination would not interfere with operations and without addition proof I would Reject.