THE MBTA ISSUED a request for proposals last Friday for its planned privatization of three bus maintenance garages located in Quincy, Lynn, and Boston, a move that has put the agency on a collision course with T unions opposed to the outsourcing.

T officials said at a briefing for reporters on Monday that they believe bus maintenance costs can be lowered from $47 an hour to $27 per hour. “We’ve been going through a process trying to make our bus maintenance work more efficiently,” said MBTA interim general manager Steve Poftak.

Poftak said the T has already been able to implement management changes in other areas resulting in “about $8.8 million in cash savings.”

Those savings leave the agency $12.2 million short of the savings goal set by its Fiscal and Management Control Board, which the T hopes to cover through privatizing its bus maintenance garages. However, the MBTA leadership was unable to provide a projection Monday of annual savings on bus maintenance if potential bidders met the $27 per hour target cost the T has identified.

T officials defended the decision to privatize the garages, which has sparked sharp criticism and pushback from union workers and state lawmakers, citing an arbitration ruling released late last month. The ruling came in a separate case involving the T and the Carmen’s Union over privatization of the T’s money room in late 2016 and warehouse operations beginning in February of this year.

The T has realized significant savings since the privatization of both operations. According to a report presented at the briefing, the money room, where the T’s cash flow is managed, saw a 65 percent reduction in annual costs, down from $11.8 million to $3.6 million in fiscal year 2016. Meanwhile, warehouse operations are on track to experience a 40 percent annual cost reduction, down from annual costs of $12.1 million to $7.1 million.

In terms of workplace efficiency, the T reported improvement in both areas: An 80 percent reduction in deposit time for cash collections managed under the privatization agreement with Brinks, and a compliance rate of 99.8 percent for deliveries by warehouse contractor Mancon within the 10-hour delivery standard.

The Carmen’s Union filed a grievance last year in accordance with section 13c of the Urban Mass Transportation Act of 1964, claiming the T violated the federal act when it decided to outsource the money room and warehouse tire shop without negotiating with the union. But a ruling on the arbitration, received by MBTA officials in late June, sided with the T and said the outsourcing did not represent a violation of the federal transportation act.

MBTA general counsel John Englander said neither the money room nor warehouse outsourcing was carried out using federal funds, which meant the T was free to contract out their operations without negotiating with the union.

He said the ruling should apply to any similar challenge that might be filed by Local 264 of the machinists union regarding outsourcing of the bus garages. “The money that we use for bus maintenance is operating expense paid by the state. No federal funds are involved, so there will not be a 13c issue associated with it,” said Englander.

Local 264 business representative Mike Vartabedian declined to comment on any possible legal action from the workers, but said that the union will continue its campaign against the privatization of the bus maintenance garages. He also said T officials have yet to offer a counter-proposal to the union’s offer of up to $29 million in savings and concessions in negotiations if the T does not privatize the garages.

“We’re going to let people hear our story,” Vartabedian said. “It’s not right for the government to do this [privatize] without thinking of the consequences it will have on the riders and workers.”