On May 11, 2020, service between Bois-Franc and Montreal Central Station was closed due to the construction of Réseau express métropolitain (REM).

[7] In 2016, an average of 30,700 people rode this train daily, having almost as many passengers as Montreal's four other commuter railway lines combined.

[8] On April 22, 2016, it was announced that the Deux-Montagnes line would be converted from commuter rail to automated light metro in 2020, as part of the Réseau express métropolitain network.

The Quebec Ministry of Transport considered using the line for a high-speed connection to Mirabel Airport (Transport rapide régional aéroportuaire Montréal Mirabel, 1974) or as the first line of a BART-style regional metro system (Réseau express de Montréal, 1977; Métro régional, 1979).

In 1982, management of commuter trains was transferred to the publicly owned Montreal Urban Community Transit Commission (STCUM).

The STCUM set fares and schedules, while the Canadian National retained ownership of the equipment (passenger cars and locomotives).

CN continued to provide the tracks, stations, storage, maintenance, and train crews needed to keep the line running.

In 1992, the government of Quebec announced a modernisation plan for the line which would include electrifying the entire line at 25 kV AC (and converting the existing catenary in the Mont-Royal Tunnel to this voltage), 58 state-of-the-art MR-90 electric multiple unit trains built by Bombardier Transportation, new tracks, and centralised traffic control.

The last of the old rolling stock left Central Station at 6:30 p.m. on June 2, 1995 – 76 years, 8 months, 11 days, and ten hours after it first went into service.

Eliminating the long-standing East Junction level crossing, CN built a railway overpass to route its Saint-Laurent subdivision over the commuter train line just south of Montpellier station.

To ease overcrowding and attract new users on the Deux-Montagnes Line, the ARTM planned several projects: Under the Réseau express métropolitain project, the Deux-Montagnes line is being converted to driverless light metro operation and extended past Downtown and over the St-Lawrence to Brossard; two southwest branches will also be added, to Montreal-Pierre Eliott Trudeau International Airport and to Sainte-Anne-de-Bellevue.

[3] On December 31, 2020, the rest of the Deux-Montagnes line closed permanently in favour of REM service which will operate along the same route.

[19] The line ran through the Mount Royal Tunnel, to connect downtown Montreal, to the north side rail subdivision.