Firms that prepared an engineering study of a Metrorail tunnel under Tysons Corner are firing back at a withering critique of their work, rebutting a consulting firm and officials who they believe unfairly dismissed their analysis.

The feud over the report, which charts how a 3.4-mile stretch of the $4 billion Dulles Corridor Metrorail Project could run under Tyson Corner, mirrors the larger fight over whether a Metro line to Dulles should run underground or on an overhead rail. Supporters of the underground option have been rallying to resurrect the idea after Gov. Tim Kaine abandoned it in September. They commissioned the multimillion-dollar engineering study from three firms — Arup, Dr. Sauer Corp. and KGP Design Studio — to prove the tunnel could indeed be constructed at a reasonable price.