This chapter shall be applicable to:
a. All municipal agencies and to the public employees and public employee organizations thereof;
b. any agency or public employer, and the public employees and public employee organizations thereof, which have been made subject to this chapter by state law;
c. any other public employer, and to the public employees and public employee organizations thereof, upon the election by the public employer or the head thereof by executive order of the chief executive officer to make this chapter applicable, subject to approval by the mayor, provided, however, that any such election by the New York city board of education shall not include any teacher as defined in section 13-501 of the administrative code or any employee who works in that capacity or any paraprofessional employees with teaching functions; and
d. any public employer, and the public employees and public employee organizations thereof, to whom the provisions of this chapter are made applicable pursuant to paragraph four of subdivision c of section 12-309 of this chapter.