N.Y. Workers' Comp. Law § 62
Each plan shall have at least two municipal corporations as participants. The county shall be one of the participants in a plan. Any contract agency or contract association with the approval of the county government and any other public corporation may by resolution of its governing body elect to become a participant in a plan established in the county, or, in the case of a public corporation or contract agency or contract association located in more than one county, in a plan established in one of such counties; provided, however, that the rules and regulations adopted pursuant to section sixty-five of this chapter may exclude from participation in a plan any type of public corporation or contract agency or contract association other than the county and cities, towns and villages.
N.Y. Work. Comp. Law § 62