"700.9(B) Wiring.
Wiring from an emergency source or emergency sourec distribution overrent protection to emergency loads shall be kept entirely independent of all other wiring and equipment,"
Webster's 11th edition.
Separate: to set or keep apart
314.28(D). Permanent Barriers.
where permanent barriers are installed in a box, each section shall be considered as a separate box.
Taking the literal meaning of the definitions and the wording used in the two sections above, I would think a permanent barrier serves the purpose intended...to keep the wiring separate and apart.
I would accept a barrier based on this information.