A law firm pursuing a suit against Uber Technologies Inc. claims it found new evidence supporting its argument that it shouldn't be disqualified from the case because of the work one of its lawyers handled while working alongside the ride sharing company in a prior gig with the Chamber of Commerce.

The source of the evidence? Declarations in a new suit filed against the law firm by Uber's biggest rival, Lyft Inc.

The labyrinthine tale of the former Chamber-lawyer-turned-plaintiffs lawyer now in the crosshairs of both Uber and Lyft didn't really get underway until September. That's when lawyers from Keller Lenkner, including former Chamber lawyer Warren Postman, filed suit claiming that the way Uber classifies its drivers as contractors allows the company to unfairly compete with the firm's client, Studio City, California-based livery service Diva Limousine Ltd.

Lawyers for Uber at Morgan, Lewis & Bockius, in turn, have argued that Keller Lenkner should be disqualified from handling the lawsuit because Postman had access to “privileged and confidential” Uber information when litigating alongside the company in a case where the Chamber challenged a Seattle ordinance aiming to allow independent contractors such as Uber drivers to collectively bargain.

In the run-up to a hearing on Uber's motion to disqualify, Lyft and its lawyers atKeker, Van Nest  & Peters filed a declaratory judgment and preliminary injunction complaint against Postman and the Keller Lenkner firm Nov. 16, the Friday before Thanksgiving. Lyft's suit asked that the firm and Postman be barred from pursuing all worker misclassification claims against Lyft, claiming that Postman had a duty of confidence to Lyft because of his “common-interest” work with the company, including the Seattle litigation. The suit also sought compensatory, punitive and consequential damages “in an amount well-exceeding $75,000.”

In the Lyft action, the Keker lawyers filed declarations by lawyers who worked with Postman at the Chamber who detailed the funding and information-sharing relationship the Chamber had with Lyft regarding the Seattle case.

In court papers filed Wednesday, the Keller Lenkner lawyers attempted to wield those declarations to argue that Postman only had access to “public facts or legal framing” in the Seattle litigation—types of information that they say don't support disqualification under California law.

“The new evidence of Lyft's involvement in the case confirms counsel's implicit concession: non-public facts critical to this case were not shared,” wrote the Keller Lenkner lawyers. “Uber would never—let alone 'normally'—have shared such information when it knew that the Chamber was regularly communicating with Lyft about the case; that the Chamber was represented by Lyft's longtime counsel, Jones Day; and that Lyft was paying the Chamber's legal bills.”

Reached Wednesday, Travis Lenkner declined to comment beyond the court papers.

Uber's lawyer, Brian Rocca of Morgan Lewis, and Lyft's lawyer, Keker's Rachael Meny, didn't immediately respond to messages seeking comment.