N.Y. RPT Law § 429

§ 429. Real property used for professional major league sports. Real\nproperty within a city having a population of one million or more, used\nby both a professional major league hockey team which is a member of the\nNational Hockey League and a professional major league basketball team\nwhich is a member of the National Basketball Association to play their\nhome games shall be exempt from taxation to the extent said taxes are\nthe obligation by lease or otherwise of the owners of franchises for\nsuch teams, provided that such owners enter into a written agreement\nwith the chief executive officer of the municipality in which such\nproperty is located to play their home games within such municipality\nfor a period of at least ten consecutive years. The tax exemption\nprovided herein shall be granted to real property being used, in whole\nor in part, for the aforesaid purposes on the date such agreement is\nexecuted and shall apply to taxes which become due and payable after the\naforestated agreement is executed and shall continue with respect to\nsuch property as long as both of said teams play their home games\ntherein and no longer. Such exemption shall not apply with respect to\nany improvement to such property made after the date such agreement is\nexecuted which improvement is not used for the provision of facilities\nor services related to sports, entertainment, expositions, conventions\nor trade shows. If one or both of said teams shall cease to play their\nhome games in said property at any time, the tax exemption provided\nherein shall cease immediately and such property shall immediately be\nrestored to the tax rolls and thereupon become subject to taxation and\nshall be taxed pro rata for the unexpired portion of the taxable year.\n