A work permit or equipment use permit is generally not required to install a common window AC unit, unless the unit exceeds three tons/36,000 BTU/hr.
But it also states:
Follow the manufacturer’s instructions.
Make sure the unit is installed securely. Support the unit from underneath, or firmly fasten it from inside with angles. You may use metal brackets, mounting rails, etc.
Local Law 11 is posted athttp://www.nyc.gov/html/dob/downloads/pdf/locallaw_11-1998.pdf
and it states:
(d) Necessary repairs.-(1) Unsafe condition. a. Upon the filing of the architect
's or engineer's report of an unsafe condition with the commissioner, the owner, his or her agent or the person in charge shall immediately commence such repairs or
reinforcements and shall undertake such measures as may be required to secure public safety and to make the building's exterior walls or appurtenances thereof conform to the provisions of this code.
b. All unsafe conditions shall be corrected within thirty days of the filing of the critical examination report.
c. The architect or engineer shall inspect the premises and file an amended report setting forth the condition of the building within two weeks after repairs to correct the unsafe condition have been completed.
My opinion is that you have to get brackets installed if the inspector or the building management said they are required.
I am sorry this is probably not the answer you had hoped for, but it would be a disservice to you, and unprofessional of me, not to provide accurate information.
I hope this information is helpful.