Suffolk Construction is “no longer compelled to stay silent” on the state service plaza contract controversy, the company said Thursday, issuing affidavits in its defense, requests for information, and urging MassDOT not to give the contract to losing bidder Global Partners. Suffolk partnered with Ireland-based Applegreen in a bid for a contract for the long-term lease and management of 18 MassDOT highway service plazas. Applegreen was awarded the bid, but after a losing bidder, Waltham-based Global Partners, alleged improper communications between the companies and MassDOT, they withdrew from the process. State officials have not yet said whether they will rebid the contract or hand it to Global Partners, which had the second-place bid. Suffolk filed several affidavits from executives in the case on Wednesday, vehemently denying any improper communications between them and MassDOT officials.