In the case of any employer other than the state, any of its political
subdivisions or any school district, this subdivision shall not apply
where the uniform application of terms and conditions of attendance to
employees is essential to prevent undue economic hardship to the
employer. In any proceeding in which the applicability of this
subdivision is in issue, the burden of proof shall be upon the employer.
If any question shall arise whether a particular position or class of
positions is excepted from this subdivision by this paragraph, such
question may be referred in writing by any party claimed to be
aggrieved, in the case of any position of employment by the state or any
of its political subdivisions, except by any school district, to the
civil service commission, in the case of any position of employment by
any school district, to the commissioner of education, who shall
determine such question and in the case of any other employer, a party
claiming to be aggrieved may file a complaint with the division pursuant
to this article. Any such determination by the civil service commission
shall be reviewable in the manner provided by article seventy-eight of
the civil practice law and rules and any such determination by the
commissioner of education shall be reviewable in the manner and to the
same extent as other determinations of the commissioner under section
three hundred ten of the education law.