The lawsuit alleges that Areas USA and the state negotiated terms during the bid process, while HMSHost was not given that opportunity. Areas USA, a Miami-based company, won the bid last month.
The Maryland Board of Public Works is scheduled to vote Wednesday on the contract.
The state was looking for a company to build new structures on the grounds of the existing plazas — Maryland House in Harford County and Chesapeake House in Cecil County — and split the revenue from their operations for the next 35 years, generating millions of dollars for the state.
"There is no reason to rush this decision. It is an important 35-year agreement with the state, and the final award should come from a process that is conducted with integrity," said Michael Jones, HMSHost's vice president of business development, in a statement.
The pair of travel plazas north of Baltimore are among the busiest in the nation, and the state collects millions of dollars a year from their operations. HMSHost has operated the plazas for the state since 1987.
In court papers, HMSHost asked a Montgomery County circuit judge to order the state to halt the project's approval and start a new procurement process.
Named as defendants in the HMSHost lawsuit were the Maryland Transportation Authority; the state Board of Public Works; Areas USA; and Maryland Energy Centers LLC.
HMSHost's lawsuit lacks merit and is "merely a delaying tactic," Areas' CEO, Xavier Rabell, said in a statement. "The filing is riddled with factual inaccuracies and misleading statements that we look forward to bringing to the court's attention."
The Maryland Transportation Authority declined to comment on the lawsuit, according to spokeswoman Cheryl Sparks.
HMSHost's filing came about the same time Friday afternoon that Areas held a briefing in Baltimore for the news media on the details of its winning bid.
Officials with Areas, along with its builder and architects, showed architect's renderings and said the $56 million construction budget — which the company would pay out of its own pocket — was lower than its two competitors partly because it was doing less site demolition and removing fewer trees. Other project costs are adding $9 million to the $56 million tab for Areas, company officials said.
"This has been the fairest, clearest, most open process I've been involved with," said Adam A. Gross, a principal with Ayers Saint Gross, the Baltimore-based architectural firm on the project.
Eduardo Uribe, vice president of business development for Areas, said the company operates concessions in several major U.S. airports and is building highway travel plazas in Florida. Florida officials recently expressed concern that Areas was falling behind on the project, but Uribe said the company is "on target."
The Maryland project would be Areas' second U.S. travel plaza project, Uribe said.
He said Maryland would receive 10 percent of the plazas' food sales — a percentage that could increase over time — and a tiny portion of gasoline sales.
He estimated that the plazas would generate annual revenue of more than $50 million, of which the state would receive $5 million to $6 million annually in the first years of the contract. Areas expects to turn a profit of about 15 percent, Uribe said.
Areas projects that the state could earn up to $488 million over the 35 years the company would operate the plazas.
The HMSHost lawsuit is the company's latest protest of the bidding process. It previously filed a protest with the Maryland Transportation Authority asserting that bid specifications to replace the plazas were vague and that Areas was the only bidder allowed to modify its offer. The other losing bidder, Airport Plazas/Tichman Construction Corp., joined that protest.
The Maryland Transportation Authority rejected the protest.
The contract dispute pits a large, Maryland-based company against state government over the decision to hire an out-of-state competitor. Both companies are owned by foreign conglomerates — Areas by Areas SA in Spain and HMSHost by an Italian company, Autogrill S.p.A.
The Maryland Transportation Authority and the Department of Legislative Services each recommended the deal with Areas.
Baltimore Sun reporter Candus Thomson contributed to this article.