Does the building only have a single means of egress? IBC 1008.3.2 states:
1008.3.2 Buildings that require two or more means of egress.
In the event of power supply failure in buildings that require two or more means of egress, an emergency electrical system shall automatically illuminate all of the following areas:
1. Interior
exit access stairways and ramps.
2. Interior and exterior
exit stairways and ramps.
3.
Exit passageways.
4. Vestibules and areas on the level of discharge used for
exit discharge in accordance with Section 1028.1.
5. Exterior landings as required by Section 1010.1.6 for
exit doorways that lead directly to the
exit discharge.
It sounds pretty silly to me that an AHJ would call for LESS emergency lighting, especially in a building which more than likely requires at least two means of egress. But perhaps there is a good reason for not wanting extra emergency lighting in an area that is not intended to be used as a means of egress. They seem to already have the means of egress picked out that lead directly to the exterior of the building.
Determining the exit routes, their required number, and where they lead would be in accordance with OSHA 1910.36 & NFPA 101 Article 7. These were probably hashed out with your local Fire Marshal and are based on occupancy and physical layout of the structure.
Is the stairway (with the lights they want gone) a self-contained stairway with fire doors to enter it at each level, or is it an open stairway central to the building? They may want only emergency lighting that will direct occupants towards the outer edge of the building (
where there will be purpose-built exit stairways with fire doors and made from fire-resistant materials with 1 hour of fire resistance for a 3-story or less building) as opposed to a central stairway deeper into the building. Not all stairways are created equal, and not all stairways meet the definition of an "Exit" according to OSHA 1910.36 & NFPA 101 Article 7.
Definitions from NFPA 101:
Means Of Egress: A continuous and unobstructed way of travel from any point in a building or structure to a public way consisting of three separate and distinct parts: (1) the
exit access, (2) the
exit, and (3) the
exit discharge.
Exit: That portion of a
means of egress that is separated from all other spaces of the building or structure by construction, location, or equipment as required to provide a protected way of travel to the exit discharge.
www.osha.gov