Railroad Antitrust Enforcement Act of 2015

Amends the Clayton Act to grant the United States exclusive authority to bring suit for injunctive relief against any common carrier that is not a rail common carrier and that is subject to the jurisdiction of the Surface Transportation Board (STB). This covers motor carriers, water carriers, brokers, freight forwarders, and pipeline carriers.

Declares that, in any civil action against a rail common carrier, the U.S. district court shall not be required to defer to the primary jurisdiction of the STB.

Empowers the Federal Trade Commission to regulate, and engage in antitrust enforcement regarding, collective rate agreements and certain transactions, including railroad mergers and acquisitions.

Permits treble damages against common carrier railroads in antitrust suits to parties injured by antitrust violations without regard to whether such railroads have filed rates or whether a complaint challenging rates has been filed.

Amends federal transportation law to terminate the exemptions from antitrust laws for collective ratemaking agreements.

Requires the STB, when reviewing a proposed agreement, to take into account its impact upon shippers, consumers, and affected communities.

Exempts from antitrust law the pooling of railroad cars approved by the STB or its predecessor agency.