Union leaders and their Beacon Hill allies railed against the MBTA’s proposal to hire private companies to run the upcoming bus expansion.

“We’ve seen time and time again that this has not worked,” state Sen. Michael Brady, D-Brockton, told the MBTA’s Fiscal & Management Control Board on Monday

The T is adding 60 new buses, and the cash-strapped transit agency is weighing whether to use current staff to operate or maintain them, or whether it makes more sense or to contract that work out. Two weeks ago, when T officials first brought up the idea of bidding that work out, they said they expect a decision in February, with the buses hitting the road in about a year.

Union rep Michael Vartabedian, who showed up with members of his Machinists Local 264, said, “How are they going to make that profit if it’s not in cutting corners, cutting service and taking from the workers?”

Vartebedian, citing current contracted work such as the Commuter Rail, said, “Don’t strap the MBTA with another Keolis.”

The T didn’t vote on the matter on Monday, and T General Manager Steve Poftak said a decision is expected “over the coming months.”

Poftak told reporters that he understands the frustration and acknowledges that many of the maintenance garages are in “difficult” shape, making working conditions tough. But he insisted that this wouldn’t cost current union members their jobs.

“We are within our contractual rights to explore that option,” Poftak insisted. “No one will be losing their jobs in either scenario here … head count here is climbing at the MBTA”

He said the waiver from the “Pacheco law” that the governor gave the T from 2015 to 2018, allowing the agency to contract out more work, “has been a benefit to the MBTA.”

Jim Evers, the new president of the Carmen’s Union, said, “Privatization isn’t the answer for our public transportation system.”

“The MBTA has an experienced, seasoned, committed workforce,” said state Sen. John Keenan of Quincy, who fired up the crowd, drawing whoops and a standing ovation from some. “Despite terrible working conditions … they did the work every day and their record surpasses anything you can get through privatizing.”

“I urge the board to recognize the value of its workforce,” said Taunton Democrat state Sen. Marc Pacheco, a union supporter influential enough that a state law against privatization bears his name. He said privatization is an “unnecessary gamble with a long history of failure.”