The Enquirer understands the O’Rourke team was given the good news late last week ahead of an imminent official announcement.
A source close to the talks said: “It’s been a real battle between the two bidders but O’Rourke has come out on top and will build the hospital.”
Hospital bosses praised both firms’ final designs for the new Children’s Health Park as “absolutely outstanding” last year.
The timetable for the project has slipped several months with a preferred bidder originally due to be announced last December.
The Laing O’Rourke led Acorn Consortium will be officially confirmed shortly with construction due to get underway later this year ahead of completion in 2015.
The Acorn Consortium also contains Laing Investments, Interserve and BDP.