CP's proposed $28 billion offer to buy Norfolk Southern, disclosed in mid-November, has been spurned multiple times, setting the stage for a proxy battle.
CP said in its letter to the DOJ released on Tuesday that the "collective communication strategy" adopted by rival railroads was "likely illegal because it is anticompetitive."
However, Union Pacific Corp spokesman Aaron Hunt told Reuters on Tuesday the company had "communicated with other railroads for the purpose of petitioning the government."
"We oppose this merger and we are prepared to discuss our views with the government," he said.
Executives from U.S. railroads including UP, CSX Corp and BNSF, owned by Warren Buffett's Berkshire Hathaway Inc, told Reuters last week that Class I railroads had held limited discussions concerning the impact of a merger on the industry.
The executives stressed that any discussions they have are strictly limited by law to subjects that affect the industry.
"We're limited on what we can discuss, which is why we had inside lawyers, outside lawyers and outside lawyer consultants," BNSF chairman Matt Rose told Reuters last Thursday.
"It's being done thoughtfully and it's not secretive, it's not clandestine. We are there discussing what the potential public policy implications of this would be."
CP reiterated in its letter that there was minimal overlap between its and Norfolk's networks.
The company "ultimately concluded the unprecedented action of major competitors organizing to block a new entrant from enhancing competition to the U.S. merited the attention of the antitrust authorities," CP said in a statement accompanying the letter.
(Reporting by Nick Carey and Swetha Gopinath; Editing by Don Sebastian)
By Nick Carey
