The Better Government Association on Monday asked a judge to block Mayor Rahm Emanuel from proceeding with an express system to O’Hare International Airport before resolution of a dispute over his refusal to release underlying documents in the deal.

In a motion filed in Cook County court, the non-profit news organization asked a Judge Sanjay Tailor to bar Emanuel from signing a deal to build the system before he rules on a BGA lawsuit challenging the mayor’s authority to withhold bid and other documents detailing the criteria used to award the project to tech billionaire Elon Musk.

The BGA filed that lawsuit Aug. 10 after Emanuel lawyers declined an open records request citing an exemption in state law for “proposals and bids for any contract, grant, or agreement,” which, if released, would complicate or tip the procurement process prior to the final selection of a contractor.

The BGA lawsuit argued the city cannot invoke that exemption because Emanuel and Musk announced the $1 billion project at a press conference in June, signalling a final selection had been made.

In Monday’s filing, BGA attorney Matt Topic argued the public would lose its essential role in the procurement process if it cannot see underlying records and offer input before Emanuel signs on the dotted line.

“Here, there is an important judgment to be made as to whether whatever it is that The Boring Company proposed is actually good for the City of Chicago, and whether the competing bid is better,” Topic wrote.

A second bid was submitted by O’Hare Xpress, a five-company partnership that includes Mott MacDonald, a British engineering company that has been involved in projects tied to the express train to London’s Heathrow Airport.

Bill McCaffrey, a spokesman for the city’s Department of Law, said the Illinois legislature protected bid documents from public release until the final award of a public contract has been made. “The BGA cannot use the Freedom of Information Act to insert itself into a public procurement process,” McCaffrey said.

At their joint appearance in June, Emanuel and Musk both rejected skepticism over the feasibility and need for a new, underground express system that was said to be capable of transporting passengers from The Loop to O’Hare in 12 minutes. The CTA Blue Line already travels that route above ground, though it makes several stops and takes 40 to 50 minutes.

A swirl of unresolved issues surrounds the city’s new partnership with Musk, who in June said he could start digging by the end of this year and get the system up and running in as little as 18 months. But even the head of the Emanuel’s Chicago Infrastructure Trust, which helped green-light Musk’s venture, pegged a realistic timetable at four years.

What’s more, there is no public evidence Musk has developed, tested, or used the faster, cheaper tunnel-boring technology he claims he wants to rely on in Chicago. Musk has dug a two-mile “test” tunnel under the Los Angeles suburb of Hawthorne, but it was excavated with conventional boring equipment.

The next court hearing on the case is scheduled on December 20th.