Looking into it a bit more it looks like the project is still going forward and the plan is to put in some temporary barriers while they wait for some redevelopment to happen. I'll leave the note open as a reminder to revisit the issue, though at this point it seems likely to be pushed to next year

https://montreal.ca/articles/rues-william-saint-thomas-et-du-seminaire-travaux-dinfrastructures-56625