The story
At the time when Exo was created in 2017, the territory that this now sector covers was served by three organizations:
CIT Richelain that covered bus service for La Prairie, Candiac and Saint-Philippe (and prior to 2001 the communities that now form Saint-Jean-sur-Richelieu);
CIT Roussillon, created in 1984 and providing commuter bus service to Delson, Saint-Constant and Sainte-Catherine; and
TARSO, that offered paratransit to all of the municipalities above.
The expired contract for transport services between Transdev Limocar and CIT Roussillon was a 10-year contract that ended on July 15, 2018. In 2018, Exo awarded Transdev the contract to run service for the Richelain sector. The contract start date was January 1, 2019 and runs till June 30, 2024 with a 3-year option for exo to extend the contract till June 30, 2027.
Exo operated Roussillon and Le Richelian as their own sectors until they were merged on July 31, 2023, when the Réseau express métropolitain opened. The new sector's bus network was reconfigured to send commuters heading downtown to Panama and Brossard stations instead of Terminus Centre-Ville.
From Wikipedia’s article on Exo Richelain / Roussillon sector, shared under CC BY-SA 4.0.4