N.Y. C.P.L.R. 1013

§ 1013. Intervention by permission. Upon timely motion, any person may\nbe permitted to intervene in any action when a statute of the state\nconfers a right to intervene in the discretion of the court, or when the\nperson's claim or defense and the main action have a common question of\nlaw or fact. In exercising its discretion, the court shall consider\nwhether the intervention will unduly delay the determination of the\naction or prejudice the substantial rights of any party.\n