Some groups (including envrionment groups bizarrely) objected to the elevated rails, even though these would not split neighbourhoods the way elevated highways did in the 60s throughout north america.
The project was taken away from CDPQ who proved they can deliver transit on time and on budget in both Montreal and Vancouver and given back to STM who have a history of cost overruns. STM immediately proposed running the entire network underground and not running it into downtown, requiring a 2 seat ride onto the green line which is already over-crowded. That explodes estimated costs to $36B CDN from CDPQ's $10B and delivers fewer km of track and less function. What a mess.