New York State’s highest court on Thursday unanimously reinstated the city’s plan to expand street-hail taxi service beyond Manhattan, overturning a lower-court ruling that had stalled the action last year.

The 6-0 decision by the Court of Appeals allows the city to issue up to 18,000 “hail licenses” for livery cabs in northern Manhattan and the other boroughs, upholding a cornerstone of Mayor Michael R. Bloomberg’s taxi policy that represents a broad culture shift in the way cabs operate in New York.

The ruling also clears the way for the city to generate as much as $1 billion by auctioning off 2,000 medallions for wheelchair-accessible yellow taxis; as originally passed, the measure required that 20 percent of new vehicles be wheelchair-accessible.