Trains on the network are fully automated and driverless,[10] and the stations are completely enclosed and climate controlled, featuring platform screen doors.

[11] The line has been built by CDPQ Infra, a subsidiary of the Caisse de dépôt et placement du Québec, an institutional investor that manages various public and para-public pension plans and insurance programs in Quebec.

On 13 January 2015, Quebec premier Philippe Couillard and Michael Sabia, CEO of the Caisse de dépôt et placement du Québec (CDPQ), agreed to a partnership in which the Crown corporation could assume financing for major transportation projects in the province, with CA$7.4 billion planned to be spent on infrastructure from 2014 to 2024.

[13] On 22 April 2016, Sabia and Montreal Mayor Denis Coderre unveiled the project, then known as the Réseau électrique métropolitain, to the media.

[14] On 22 June 2016, CDPQ Infra published two requests for qualification: one for the engineering, procurement, and construction contract and the other for the rolling stock, systems, operation, and maintenance.

These new stations—Central Station, McGill, and Édouard-Montpetit—would improve downtown Montreal service by integrating the REM with the Metro system through connections to the Orange, Green and Blue Lines.

On 1 December 2017, the CDPQ extended the tender process on the project to the end of January 2018, citing a need for additional discussions with the bidders.

[24] On 10 November 2017, the date of the planned announcement of the selected contractors, the procurement process was "postponed indefinitely" to provide more time for analysis and evaluation of the bids received.

[25] On 8 February 2018, CDPQ Infra finally announced its selection: the Groupe NouvLR consortium for the EPC contract (SNC-Lavalin Grands Projets, Dragados, Aecon, Pomerleau, EBC, and AECOM) and the Groupe des Partenaires pour la Mobilité des Montréalais for the RSSOM contract (Alstom and SNC-Lavalin O&M).

[38][39] An opening ceremony was held on 28 July 2023, with Prime Minister Justin Trudeau, Premier of Quebec François Legault, Mayor of Montreal Valérie Plante, president and CEO of CDPQ Charlies Emond, and president and CEO of CDPQ Infra Jean-Marc Arbaud inaugurating the line.

[43] Within the first three days of revenue operation, the new line suffered a number of service disruptions caused by stuck railway switches and computer issues.

[49] In the third quarter of 2025, the REM will be shutdown for a period of four to six weeks to enable testing of the central section of the line which is scheduled to open by the end of the year.

[52] In August 2024, La Presse reported that CDPQ Infra refused to confirm that Griffintown–Bernard-Landry station would be completed by 2027, but that construction could take place while the REM is in operation.

The northwest branch is a conversion of the Deux-Montagnes line, with a second track added beyond Bois-Franc station and all at-grade crossings eliminated.

[67] In April 2018, a $2.8-billion contract was awarded to Alstom and SNC-Lavalin to deliver a driverless light metro, including rolling stock and automatic signalling, and to operate and maintain the line.

Across the REM, 12 pieces of permanent artwork will be installed at a cost of $7.3 million, as part of Quebec's percent for art programme.

[74] In a report prepared by the Bureau d'audiences publiques sur l'environnement [fr] (BAPE), released on 20 January 2017, CDPQ Infra was criticized for failing to provide crucial information on the project's financial model, environmental impact, and impact on ridership levels on existing public transit systems across Greater Montreal.

[75] The BAPE also stated that CDPQ Infra had not met its obligations with regard to transparency, as it had failed to provide information in a timely fashion on the ridership levels of the REM's three branches.

[76] Another controversy occurred in November 2019, when Montreal mayor Valerie Plante proposed naming Griffintown's REM station after former Quebec premier Bernard Landry, who was part of the Parti Québécois.

[84] The government also made a request to determine the best electrified transit system to be put in place for the East Island, with the possibility of it being a new REM project.

Beginning a few blocks east of Robert-Bourassa Boulevard (and therefore from Central Station), the line would have run east on an elevated guideway along René-Lévesque Boulevard and Notre-Dame Street until St-Clément Street, where it would have turned north and split into two branches: In May 2022, the project was abandoned,[91] and as of mid-2023, nothing has been announced about its eventual replacement, which is under study, except that it is to be named Projet structurant de l’Est (PSE) instead of REM.

[92] In partnership with the City of Longueuil and the Municipality of Brossard, the Quebec government announced a proposed extension of the REM through the South Shore of Montreal.

Fournier added that the segments of REM 2.0 along Taschereau Boulevard would be elevated, while the portions along the Quebec Route 132 would be at ground level to service Old Longueuil and beyond.

[96][97] Following the REM's inauguration, Fournier held an interview with La Presse where she indicated that she had taken part in continued conversation with Quebec's Minister of Transport, Geneviève Guilbault, who reiterated the province's interest in the project and stated that the extension was under study.

[101] The mayor indicated that the city was designing its future downtown with a lighter mode of public transit to test the feasibility of the REM model and sought to keep the municipality's voice in the conversation.

[102] In response to this announcement, Fournier commented that she was supportive of the Taschereau REM project but that Longueuil had not received an update from CDPQ Infra for over a year and a half.

On January 29, 2024, CDPQ Infra announced that it was withdrawing from the proposed extension, leaving local mayors to coordinate any future development of Taschereau Boulevard with the soon-to-be-created provincial government agency for large public transit projects.