N.Y.C. Admin. Code § 24-318: § 24-318 Validity of lien; grounds for challenge.

a. In any proceedings to enforce or discharge a lien created pursuant to section 24-317 of this subchapter, the validity of the lien shall not be subject to challenge based on:

(1) The lawfulness of the work done; or

(2) The propriety and accuracy of the items of expenses for which a lien is claimed, except as provided in this section.

b. No such challenge may be made except by (1) the owner of the property, or (2) a mortgagee or lienor whose mortgage or lien would, but for the provisions of section 24-317 of this subchapter, have priority over the department's lien.