The stations reopened later in the evening and service resumed, she said.
As many as 20,000 households across New York City and Westchester County were not expected to be back online by the weekend because of damage to their homes' electrical systems, officials said.
Contractors will need to check the electrical wiring in each home and business to ensure that power can be safely restored, Bloomberg said. Salt-caked wiring could ignite once the power is restored.
On Long Island's hard-hit coast, towns such as Oceanside remained largely without power.
"The lights came on for three minutes here. Everybody cheered like A-Rod (Alex Rodriguez) hit one out at Yankee Stadium," said Rick Wolkenberg. "Then there was this weird hum and everything went out again. They teased us, and now we're sitting here in the dark again."
The 59-year-old mortgage lender said his staff has been working for days in his office by means of a small generator and flashlights.
"Everyone's really frazzled, angry," he said. "It's not just the power. Now it's getting an electrician to evaluate the house, then getting a plumber -- and nobody's coming because they're all overwhelmed."
His 81-year-old mother, Edith, moved in with his family after Sandy slammed through her home in Oceanside.
"There just seems so many obstacles now," Wolkenberg said.
"It is like a war zone down there," Gov. Chris Christie said, referring to places such as Ocean County's Mantoloking, where flooding and fires wiped out large sections of the town last week.
At least 20 homes burned to the ground there, mirroring an incident in Breezy Point, a Queens neighborhood where a cluster of more than 100 houses caught fire during the storm.
"We don't know what to expect for the flooding situation as the shorelines have been changed," Christie said. "For many of them, the dunes are gone. So, moderate flooding under normal conditions becomes major in these conditions."
More than three-fourths of New Jersey's school systems were operating Wednesday and 1,728 public schools were open in New York.
Elsewhere, there were signs of the region rebounding.
The PATH train between New Jersey and New York resumed limited service under the Hudson River on Tuesday, after being shut ahead of the storm.
Commuter traffic reopened Wednesday in the Holland Tunnel, where about 91,000 vehicles typically pass under the Hudson River between Manhattan and Jersey City, New Jersey.
Air travel continued to be affected. Authorities advised air travelers to check with their carriers ahead of the storm.
"Airlines serving the Port Authority's major airports -- Newark Liberty International, John F. Kennedy International and LaGuardia -- have canceled all or a significant number of their flights beginning at noon today and continuing through early tomorrow," the Port Authority of New York and New Jersey said Wednesday in a statement.