It is an AHJ call and I would say No an accessible egress is not required.
3401.6 Alternative compliance.
Work performed in accordance with the International Existing Building Code shall be deemed to comply with the provisions of this chapter.
3408.1 Conformance.
No change shall be made in the use or occupancy of any building that would place the building in a different division of the same group of occupancies or in a different group of occupancies, unless such building is made to comply with the requirements of this code for such division or group of occupancies. Subject to the approval of the building official, the use or occupancy of existing buildings shall be permitted to be changed and the building is allowed to be occupied for purposes in other groups without conforming to all the requirements of this code for those groups, provided the new or proposed use is less hazardous, based on life and fire risk, than the existing use.
IEBC
1012.8 Accessibility.
Existing buildings that undergo a change of group or occupancy classification shall comply with this section.
Exception: Type B dwelling or sleeping units required by Section 1107 of the International Building Code are not required to be provided in existing buildings and facilities undergoing a change of occupancy in conjunction with less than a Level 3 alteration.
1012.8.1 Partial change in occupancy.
Where a portion of the building is changed to a new occupancy classification, any alteration shall comply with Sections 705, 806 and 906, as applicable.
1012.8.2 Complete change of occupancy.
Where an entire building undergoes a change of occupancy, it shall comply with Section 1012.8.1 and shall have all of the following accessible features:
1. At least one accessible building entrance.
2. At least one accessible route from an accessible building entrance to primary function areas.
3. Signage complying with Section 1110 of the International Building Code.
4. Accessible parking, where parking is provided.
5. At least one accessible passenger loading zone, where loading zones are provided.
6. At least one accessible route connecting accessible parking and accessible passenger loading zones to an accessible entrance.
Accessible egress not required Section 1012.8.1 sends you to Section 705
705.1 General.
A facility that is altered shall comply with the applicable provisions in Sections 705.1.1 through 705.1.14, and Chapter 11 of the International Building Code unless it is technically infeasible. Where compliance with this section is technically infeasible, the alteration shall provide access to the maximum extent that is technically feasible.
A facility that is constructed or altered to be accessible shall be maintained accessible during occupancy.
Exceptions:
1. The altered element or space is not required to be on an accessible route unless required by Section 705.2.
2. Accessible means of egress required by Chapter 10 of the International Building Code are not required to be provided in existing facilities.
Specifically not required