The EPO's I have done are more for Fire and Smoke rather than
just the UPS. Often are tied into seperate smoke dampers and duct detectors and seperate priority on the building fire system, so a fire drill wont drop the system. I take a circuit from the UPS to power a relay that when dropped out will open the EPO contacts for the UPS, and close the dampers, the a trouble signal to the fire system. Heat det.s DD's and smokes are seperate in the room for a full alarm. For the switch I use a 22mm guarded at the door, with a momentary key reset for the relay. (Much more expensive than a single ploe switch!)
Anyway, the way I understand it.... It's all completely unnessesary unless there is air/smoke interconnection to the rest of the building. The room is supposed to be fire-rate either way, and have smoke detection in the very least. But if the batteries are vented, or if the room ties to any outside HVAC, then the EPO for the batteries, and HVAC is required by the Fire Inspector more than the Electrical Inspector. And, here at least, it is the Fire Inspector that will ask for the operation of the EPO, I guess the had a battery fire a while back, and this is now a pet peev.
Anyway, here some commentary, (Not code) on it...
In 645.10, two separate disconnecting means are required, but a single control, such as one pushbutton, is permitted to electrically operate both disconnecting means. The disconnecting means is required to disconnect the conductors of each circuit from their supply source and close all required fire/smoke dampers. (See the definition of disconnecting means in Article 100.) The disconnecting means is permitted to be remote-controlled switching devices, such as relays, with pushbutton stations at the principal exit doors. The 2002 Code specifies that the actuation of the emergency pushbutton(s) be accomplished by pushing the button in, rather than pulling it out. The requirement recognizes that in an emergency situation the intuitive reaction to operating the control is to push, not pull, the button.
The requirements of 645.10 and those of 645.7 for sealing penetrations are intended to minimize the passage of smoke or fire to other parts of the building.