UP spokeswoman Raquel Espinoza declined to comment on the lawsuit or its dismissal.
After the lawsuit was filed in 2011 in a federal court in Washington, D.C., both railroads defended their pricing practices and denied the lawsuit's allegation.
The lawsuit was dismissed without prejudice, meaning Oxbow can refile the complaint.
Attorneys for Oxbow did not immediately return messages left Friday, but Oxbow spokesman Brad Goldstein said the company will refile the lawsuit, amended to reflect the judge's concerns."Oxbow ... will move forward to hold UP and BNSF accountable for their illegal and anti-competitive behavior," Goldstein said. Union Pacific is headquartered in Omaha, Neb. BNSF is based in Fort Worth, Texas, but is part of Warren Buffett's Omaha-based Berkshire Hathaway Inc.