So only days after NIMBYs have tried to have the REM de l'Est/REM2 cancelled for ideological reasons, the REM3 line has had clarifications made on it since there was uncertainty around it. First is that it is an automated grade separated light rail system rather then a tram, it'll be above ground rather then ground level (which is to be expected if it isn't a tram) and will be a 13 kilometre line connecting the Panama bus terminal/REM station up to the Longueuil metro station/bus terminal along Taschreau Boulavard and then go up to College Edouard-Montpetit through Vieux Longeuil. It will not have wired power like REM1 and REM2, meaning it will almost certainly use a third rail to power it. No budget has been mentioned but based on the cost of REM1 and REM2 it'll likely cost around 2 billion due to most of it being above ground but the part in Vieux Longuil likely being underground, but capable of rip and cover construction. No timetable for construction has been announced. French article for those who want to/can read it, I couldn't find an English one:

https://www.lapresse.ca/actualites/2022-02-14/legault-promet-un-tres-beau-prolongement-du-rem-sur-la-rive-sud.php