You are correct that the IFC doesn't require that they be functional. However, IPMC clearly states that ALL devices be maintained in accordance with the IFC. It DOES NOT say that all devices required by the IFC be maintained.Your scenario above does create an issue. The issue of 1st amendment rights vs. property maintenance is a fine line. IF I ever had to deal with this situation, which I doubt I will, my stance would be the following:
The smoke alarms were not intended to be used as smoke alarms when installed. IFC 807 will need to be complied with. It shall be obvious that the smoke alarms are intended to be art and not functioning smoke alarms. The method of achieving this obvious intent shall be approved. A single smoke alarm in the middle of a ceiling which has not had it's appearance altered will not be accepted. It is my opinion that the method of display should reveal the intent to the untrained person.
Now a question for you. At which point does a non-functioning fire extinguisher in a structure become art or a collectable? Is a non-functional fire extinguisher hanging on a wall bracket considered art? The identical fire extinguisher is hanging on an identical bracket less than five feet away. That one is required by IFC and functional. To the untrained eye, in an emergency situation, they look identical. The building occupant, who is a 9/11/01 buff, calls it a memorial to the lost fire fighters at ground zero.