rktect1 - I would reference the following 2008 NEC Section (and would assume that this is more restrictive than than 1008.1.9 of the IBC):
2008 NEC:
110.26 © (3) Personnel Doors. Where equipment rated 1200A or more that contains overcurrent devices, switching devices, or control devices is installed and there is a personnel door(s) intended for entrance to an egress from the working space less than 7.6 m (25 ft) from the nearest edge of the working space, the door(s) shall open in the direction of egress and be equipped with panic bars, pressure plates, or other devices that are normally latched but open under simple pressure.
Sounds like the NEC is the more restrictive of the two codes in this case, and therefore would make 1008.1.1 (Door Size), 1008.1.8.3 (Locks and Latches), and 1008.1.8.4 (Bolt Locks) of the IBC (2006).
1008.1.9 (Panic and fire exit hardware) of the IBC mirrors the NEC with the following paragraph: Electrical rooms with equipment rated 1,200 amperes or more and over 6 feet (1829 mm) wide, that contain overcurrent devices, switching devices, or control devices with exit access doors must be equipped with panic hardware and doors must swing in the direction of egress.
RGLA - In our jurisdiction, the NEC requirement would require any personnell doors within the 25 feet to have panic hardware, mullion or not.