E-ZPass readers and cameras are in place to start New York City’s congestion pricing program on Jan. 5.

Gov. Kathy Hochul, who blocked the program just weeks before its original start in June, is on board this time. Federal transportation officials have signed off. And the region’s mass transit system is still counting on the billions of dollars that are expected to be generated through new tolls to drive into the busiest parts of Manhattan.

But even as congestion pricing seems like it is happening for real this time, it could still unravel at the last minute because of a flurry of legal challenges, including from the State of New Jersey; Vito J. Fossella, the Staten Island borough president; and the United Federation of Teachers.

At least 10 lawsuits have been brought against the tolling program in federal and state courts in New York and New Jersey in recent years. Plaintiffs in those cases have argued that the new tolls would be a financial burden for commuters, hurt small businesses, and shift traffic and pollution to other parts of the city and region — including to disadvantaged communities like East Harlem and the South Bronx.

It is not unusual for high-profile transportation projects to land in court — and it is also not uncommon for judges to halt projects, at least temporarily. In this case, congestion pricing has already been stopped once by a politician, and its most powerful detractor, President-elect Donald J. Trump, has said he would end it permanently once he takes office next month. If a court decides on even a slight delay, it would make Mr. Trump’s promise easier to carry out.

“We’re not giving up,” said Kathryn Freed, a member of New Yorkers Against Congestion Pricing Tax, which is suing to stop the program. Ms. Freed said the tolls would contribute to an increase in the cost of goods and services, including deliveries, in the congestion zone as toll charges are passed along to customers.