Massachusetts Inspector General Jeffrey Shapiro will soon release the findings of his office’s investigation into a controversial bidding process for the redevelopment of highway service plazas across the commonwealth.

Last summer, the Massachusetts Department of Transportation awarded Ireland-based Applegreen a nearly $1 billion contract to tear down and rebuild nine rest stops and upgrade nine more, many of them along the Massachusetts Turnpike. But the deal quickly turned sour as an opposing bidder waged a monthslong public relations campaign against Applegreen. The company pulled out of the deal in September.

Speaking before lawmakers on the State Senate’s Post Audit and Oversight Committee Tuesday afternoon, Shapiro said within weeks he plans to make public an investigatory letter into the situation.

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“It won’t surprise anyone for me to say there are plenty of lessons to be learned,” Shapiro said of the contract bidding process. “To suggest in its totality that the procurement was a model procurement would simply be inaccurate.”

In June, MassDOT awarded Applegreen the 35-year contract to revamp the state’s highway service plazas. But Global Partners, a Waltham-based company that operates gas stations and retail stores across the Northeast and other parts of the United States, claimed its competitor’s bid was “never financially sound” and MassDOT unfairly favored Applegreen in its selection process. Global ultimately filed a lawsuit seeking to block the contract.

During a September meeting of MassDOT’s board of directors, Global Partners’ Chief Operating Officer Mark Romaine spoke out against the deal, alleging Applegreen violated ethics laws by texting with a committee chair.

“Your own rules are very clear,” he said in the September meeting. “If a proposer engages in prohibited contact, it is grounds for disqualification. Period.”

The next week, Applegreen backed out of the deal, citing an inability to reach “an agreement on definitive terms” with MassDOT. Applegreen also said “costly and continued litigation threats from an opposing bidder” had jeopardized the project’s timeline and financing.

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Monica Tibbits-Nutt, who at the time was Massachusetts’ transportation secretary and CEO of MassDOT, issued a statement acknowledging Applegreen was no longer the right partner for the project.

“After a comprehensive, transparent selection process, additional negotiations were always expected between MassDOT and Applegreen to provide the best possible value for taxpayers,” she said in a statement. “It is now clear that Applegreen is no longer the right partner to deliver on this project. Our focus is on moving forward to deliver the highest quality service plazas as quickly as possible for the people of Massachusetts.”

A month later, Tibbits-Nutt unexpectedly stepped down from her post. In a press release announcing the departure, Gov. Maura Healey’s office did not mention the service plaza deal controversy and said Tibbits-Nutt planned to “return to private industry.” Healey later said in a press conference that she did not ask Tibbits-Nutt to step down and that her resignation was “absolutely not” related to the service plaza controversy.

Healey tapped MBTA General Manager Phil Eng to temporarily take over as transportation secretary, while continuing to oversee the T. Four months later, Eng still holds both posts. Healey has not updated the public on her search for a permanent hire.

At the start of Tuesday’s Senate hearing, Chairman Mark Montigny announced that Eng will appear before the Post Audit and Oversight Committee on March 2.

Representatives for MassDOT and Applegreen did not immediately respond to requests for comment. Global Partners COO Mark Romaine said in an emailed statement that he welcomes the inspector general’s investigation and that Global plans to bid again when MassDOT restarts the procurement process for the service plaza project.