The Massachusetts Bay Transportation Authority announced Tuesday it had reached a new agreement with its main janitorial company to make 30 employees full time, making them eligible to receive health insurance.

The deal with S.J. Services will save the MBTA an estimated $3.7 million over the previous contract, transit officials said.

S.J. Services and a second janitorial firm contracted by the MBTA have drawn controversy by cutting the hours for dozens of their employees, making them ineligible for health insurance. At a December meeting, transit officials released figures showing that close to 80 workers for the two companies, about one-quarter of the staff, were laid off or lost health insurance when their hours were cut.

In response, the MBTA’s oversight board decided to consider new companies. S.J. Services was not one of the invited bidders but voluntarily submitted an offer that was “much better than they received back from’’ other companies, said John Englander, general counsel for the MBTA and the state Department of Transportation.

The new agreement calls for S.J. Services to add two supervisors and provide 70 more hours of cleaning services a week. It calls for the company to be fined if certain standards, such as stocking supplies, are not met.

Acting MBTA general manager Brian Shortsleeve called the new contract a win-win. The goal is to maintain cleaner stations across the system, address health care concerns for many employees, and save money, he said.

Maddie Kilgannon can be reached at maddie.kilgannon @globe.com. Follow her on Twitter @MaddieKilgannon.