N.Y. Civ. Serv. Law § 19
The administration of this chapter in a village, school district or special district incorporated or established on or after the effective date of this act and comprising territory in two or more counties, or in a public agency established on or after the effective date of this amendment and maintained jointly by two or more counties or two or more municipal corporations or other civil divisions, including school districts, situated in different counties, shall be under the jurisdiction of the civil service commission or personnel officer having jurisdiction over the classified service of one of such counties selected by action of the governing board or body of such village, school district or special district, or the appointing authority of such public agency. In the event that such board or body of such a newly incorporated village or newly established school district or special district or the appointing authority of such newly established public agency fails to make such selection within ninety days after the effective date of such incorporation or establishment, such village, school district, special district or public agency shall be subject to the jurisdiction of the civil service commission or personnel officer having jurisdiction over the classified service of the county in which the greater or greatest territorial area of such village, school district, special district or public agency is located.
N.Y. Civ. Serv. Law § 19