For each class there shall be maintained a separate departmental reemployment list within a given state agency, which shall consist of the names of persons on the general reemployment list but employed in that state agency at the time of separation. There shall also be maintained a separate subdivisional reemployment list within a given state agency which shall consist of the names of persons employed in a subdivision of a state agency at the time of separation if subdivisions for that state agency have been set up with the approval of the Department of Human Resources for layoff purposes.