The Montreal, Maine and Atlantic Railway, itself a product of the 2002 Iron Road Railways bankruptcy, filed for bankruptcy in the United States and Canada on August 7, 2013, following the fiery Lac-Mégantic rail disaster, in which a runaway crude oil train killed forty-seven people and caused an estimated $200 million in property damage to downtown Lac-Mégantic, Quebec. The company received protection under Chapter 11 of the United States Bankruptcy Code and under the Companies' Creditors Arrangement Act in Canada to oversee the sale of assets. In December 2013, Fortress Investment Group, LLC, through its subsidiary Railroad Acquisition Holdings, LLC placed a stalking horse bid on the operating rail lines, which was accepted by the bankruptcy trustee in January 2014. In February 2014 RAH announced that it had formed the CMQ to become the operating entity of the rail lines and that the sale would be concluded in March 2014. CM&Q received its certificate of fitness from the Canadian Transportation Agency on June 24, 2014. In March 2014, John E. Giles of RAH drove the length of the line, visiting communities and industries served by the railway and inspecting the condition of tracks and installations. He estimated a $10–20 million investment would be needed over three years to repair the rail line, then in poor condition and not safe for the transport of oil or dangerous goods. In the same year, the CMQR acquired 10 GMD SD40-2Fs from Canadian Pacific Railway. The company planned to resume transport of crude oil by rail in January 2016; however, this did not happen due to petroleum market conditions. On November 20, 2019, it was announced that Canadian Pacific Railway would purchase CMQ. Canadian Pacific's CEO, Keith Creel remarked that the acquisition would give CP a true coast-to-coast network across Canada and an increased presence in New England. This would result in several former CP rail lines in Maine and Quebec, which were sold over the years to CM&Q's predecessor railroads, being reacquired by CP. On June 4, 2020, CP officially finalized its acquisition of CMQ.
In September 2015, CMQ was selected by the Maine Department of Transportation to operate the state-owned Rockland Branch rail line between Brunswick and Rockland, taking over the line from previous operator Maine Eastern Railroad on January 1, 2016. The CMQ proposal did not include the operation of passenger excursions that had been operated by Maine Eastern, ending 11 years of successful passenger rail operations along the Maine coast.
