I also, normally expect that the FA contractor will provide the door holders also. iWire assumes an addressable system, which I tend to agree with, which means the control module. However, you must determine much more. If addressable, is the power for the door holders, 24VDC from the FA system, or 120VAC from conventional system. If 24VDC, then you will probably have a single module near the power supply and send 24VDC wiring from there to all devices. If 120V it could mean local at each door location with a control module at each location. If it is conventional, then you will likely have relay base smoke detectors and 120VAC locally.
Nothing is ever simple.