Democrats in the Legislature voted in 2015 to give Gov. Charlie Baker a three year exemption from a law that limits how much state agencies like the MBTA can be outsourced to private companies, but now Democrats and unions say Baker is too bent on privatization to strike a deal with workers.

"Are you ready to sit down and negotiate? You're ready to negotiate. You've been ready to negotiate since day one. You've always been willing to do that," Sen. Marc Pacheco told a crowd gathered outside the State House Wednesday to rally against plans to privatize some MBTA bus garages.

Pacheco is the namesake of the so-called Pacheco Law that limits privatization at state agencies. He was one of several Democrats who joined union leaders who say the T's management isn't negotiating in good faith with workers as they pursue privatization.

"I think it's an ideology thing.  I think that they feel they gotta privatize something and why not bus maintenance. If not bus maintenance then what's next?... To me that's not a business decision, it's a political decision," said Michael Vartabedian, the area director of the union that represents 120 bus maintenance machinists at garages Baker is considering contracting out to private companies.

But MBTA General Manager Brian Shortsleeve says he's already had three meetings with the union about the privatization plans.

"We have a very active dialogue with our employees, with all stakeholders. We're going to continue to move forward on a strategy to generate big savings for the T and deliver bus maintenance in the most effective and cost efficient way that we can," Shortsleeve told WGBH News.

Shortsleeve suggested one path the T may take would be a hybrid solution, where two-thirds of the maintenance operations remain in-house and the rest would be outsourced to "industry leading companies."

The MBTA has said it could save up to $50 million a year by outsourcing the system's nine bus garages. The T's Control Board is entertaining proposals from companies interested in taking over some or all of the work of the garages and could vote to privatize later this year.

T managers reached an accord with MBTA vehicle operators earlier this year that prevented bus driver jobs from being privatized. Bus machinist union representatives said at a rally that the Baker administration has refused to sit down at the negotiating table.

"We're looking for them to negotiate in good faith and they refuse to even meet with us so that's what we would like to see. We're willing to work with them, but they're not willing to work with us," Fletcher Hillman, a machinist in the South Boston Cabot garage told WGBH News.

Vartabedian said the bus machinists are willing to offer a savings plan that could save as much as $27 million annually, far more than the savings target set by the T's board. 

"Why wouldn't you work with that workforce and get your savings through them? Unless you had another agenda," Vartabedian said.

"The machinists know how to keep our aging machines running, which is no easy feat and I think they are experts in their field and I think we should be having real conversations before doing anything this rash," Somerville Rep. Christine Barber said at the rally.

Hillman said the bus crews are focused on safety in the shops, because if a machinist is hurt, it causes delays and incurs overtime cost to fill the shift.

"That's all we're focused on. When you start cutting corners, that suffers Service suffers,"

"Eventually what's going to happen is these buses are going to start stacking up and you know, you need people to repair them. And if they're not going to give us the people to repair them, they have to pay the overtime. It's simple math," Hillman said.