Legislative Democrats who voted to grant Gov. Charlie Baker the authority to privatize portions of the MBTA last year are having second thoughts as the T goes through with plans that could mean job changes and layoffs for union workers.

At a rally Wednesday, Sen. Marc Pacheco (D-Taunton) called for the Legislature to come back into session to repeal the portion of a 2015 law that allowed Baker to contract out MBTA services without the approval of the state auditor.

In July of 2015, the Democrat-dominated House and Senate voted overwhelmingly to allow Gov. Charlie Baker to take control of the MBTA and experiment with privatizing portions of it. In passing that year's state budget, lawmakers established the Fiscal Management Control Board, a panel hand-picked by Baker, to oversee the T. They also relaxed the Taxpayer Protection Act, the so-called "Pacheco Law," that forces private contracts to be vetted by the state auditor, giving the new board a free hand to eliminate in-house services of the T and select private companies to do the job.

Acting MBTA General Manager Brian Shortsleeve was the target of many catcalls and disparaging remarks at the Carmen's Union rally outside Faneuil Hall Wednesday. The former Bain Capital executive has been a full-throated advocate for closing the T's many budgetary woes with cost-saving contracts with private vendors.

Here are the areas the T's managers are considering booking off state payroll into the hands of private companies:

Now that the MBTA is contracting out the collection and counting of the cash fed into its fare boxes, the next step may be to eliminate the in-house workers who repair the often out-of-order Charlie Card kiosks. 

The automated fare collection equipment maintenance division "is responsible for the preventative and corrective maintenance associated with fare box, garage, fare vending and subway station fare gates system-wide, as well as ticket office equipment," according to a breakdown of MBTA divisions from 2008. The fare maintenance operation has authority of more than 3,000 pieces of equipment throughout the system.

The T is pursuing an all-new automated fare collection system, or AFC 2.0, to replace the Charlie Card kiosks. Shortsleeve has said repeatedly that the T wants to be "out of the cash business" entirely, so utilizing modern systems of mobile payment both in stations and on vehicles is a big goal.

Shortsleeve has said the T will pursue privatization plans in areas not related to the T's primary business of moving people from place to place. Warehousing for maintenance parts has long been run in-house at the T, and Shortsleeve and the Fiscal Control Board have their eyes on squeezing more efficiency from the operation by contracting it out.

"Warehouse-inventory logistics are not a core function of the MBTA. Neither are cash-management operations. These are things the private sector does very well," Shortsleeve said in June.

Privatizing the maintenance warehouse was discussed by the board in June when they requested MBTA staff determine what it would cost to bring the performance of the operation up to speed while maintaining union labor.

A three-year, $6.1 million contract with IXP Corp. would allow about a dozen unionized MBTA transit police to take on other roles instead of working the dispatch desk. The board heard the plan in July and it's supported by MBTA Transit Superintendent Richard Sullivan. The plan has not yet been voted on by the board.

One of the oldest plans on the T's drawing board has been to use private vendors to pick up many of the system's least-traveled bus routes in Boston and the surrounding towns and cities. The board heard an initial plan as soon as they first came together in 2015, but discussion of contracting out up to 65 bus routes has been minimal as the T has taken solid steps to reign in costs and attract vendors for smaller services.

Two of the senators who rallied alongside the MBTA workers of the Carmen's Union Wednesday, Transportation Chairman and state Democratic Party Chair Sen. Tom McGee and Pacheco, voted against giving Baker privatization powers when it was rolled into the budget bill by a vote of 31 to 5.

"That's the intent for my vote, to make sure that we would still keep these people's jobs," Cantwell said.

Sen. Sal DiDomenico (D-Everett) voted in favor of the powers when it was bundled into the budget bill, but says it was necessary to getting the bill passed through both chambers. 

"This is something I was totally against in the beginning, I'm against it now, I'm against it in the future," DiDomenico said after speaking to the crowd of rambunctious Carmen's Union workers and labor leaders like state AFL-CIO president Steven Tolman.

DiDomenico, the second highest ranking Democrat on the Senate budget-writing committee, said he, Senate President Stan Rosenberg and Ways and Means Chair Sen. Karen Spilka were on the same page in opposing giving Baker the privatization powers. Now he says he'd back Pacheco's effort to convince House and Senate leaders to bring the Legislature back to repeal Baker's authority to privatize.

"I would love to, and I would join him in that effort." DiDomenico said. "So I would hope that if we have a critical mass of folks who want to get this done I would be all for it and I would be one of those leaders to get this done."

McGee said he would look to his other colleagues to see "if there's a groundswell to come back this year."

"If not, that we don't come back this year, that we take it up, take this issue up again and ask the tough questions about  what are the real numbers and what are the consequences of the decisions being made," McGee said.

Removing the Pacheco Bill restrictions "has opened up the door to substantial privatization, and in my opinion has not reflected the reality of what the numbers are, and what the results are, and whether or not there's going to be real savings. And then what is the service you're going to provide?" McGee said.

A spokeswoman for DeLeo said the Speaker does not plan for the House to come back into formal session this year. A spokeswoman for Senate President Rosenberg told WGBH that the Amherst Democrat "is observing Yom Kippur and is unavailable for comment."

In 1996, Gov. William Weld proposed privatizing the entire system-wide bus operation but was shot down by Democrats who instead installed the anti-privatization rules Baker had suspended last year. Ralliers in Wednesday's crowd carried signs with the old 1990's slogan of "MBTA Privatization = A Weld Scam" with Weld's name crossed out and Baker's written over it.