From the New York Times on Thursday, in an item put together with the help of a half-dozen Times reporters ("Inaction and Delays by New York as Storm Bore Down"; bold is mine):
... Harry Nespoli, president of the Uniformed Sanitationmen’s Association, said the problems late Sunday (during the initial stages of the Northeast's post-Christmas snowstorm -- Ed.) underscored how the city could not rely on outside contractors to help with snow removal and other jobs in such storms, particularly during a holiday weekend.
“You can never count on the privates, because they don’t have to show up,” he said. “What obligation do they have? The mayor can’t order them out. The commissioner can’t order them out.”
That's quite an interesting assertion, given the following item carried in the New York Post today: