McCann was part of the BBMC consortium with Balfour Beatty and brought the action on its own after failing to land the design and build deal for the A8 dual carriageway between Belfast and Larne.
BBMC submitted the lowest bid which was rejected by the Department for Regional Development on the grounds it was abnormally low.
The BBC has reported that a High Couty Judge has now ruled the department breached public contract regulations. Compensation will be assessed at a later date.
FP McCann issued proceedings over the tender for the work it submitted in 2009.
Lawyers for the company claimed it had been unlawfully denied the work and should be entitled to damages.
The judge said there had been a clear breach of duty by the defendant in respect of its consideration of the BBMC bid.
Adjourning the case for further submissions in assessing the scale of payout, he added: “The defendant’s breach of duty should be marked by a meaningful award to reflect the loss of opportunity to the plaintiff to be awarded a significant and potentially lucrative contract.”