As per Section 2903 of the New York City Charter, the Department of Transportation does not permit the attachment of any materials to City-owned electrical equipment, including but not limited to, street light poles and poles containing electrical traffic control devices. You are permitted to install a mirror within the borders of your private property. You can also request the removal of a street parking spot to improve visibility by filing a request with the Brooklyn Department of Transportation at https://www1.nyc.gov/html/dot/html/contact/contact.shtml