I am all in for a multi-use project like this, especially where it is. This part of Hochelaga is in bad need of services, and this project would be a godsent for that (as long as the services are regular ones and not just the gentrified/gourmet version of them, like expensive Metro Plus or IGA whatever-they-are-called).
HOWEVER, (prepare your NIMBY labels), I don't see why Montreal needs 12-store high buildings. Especially when ZERO infrastructure projects are attached to the project.
Out of nowhere you will have ONE THOUSAND new families living in the same block. This will cause an explosion in the number of cars in traffic (I'm looking at you, Pie-IX, Viau, Hochelaga), demand for parking spots, Communauto cars and bike lanes, number of metro and bus users, kids in school, hospital beds, etc etc.
There is (usually) a reason for some areas of the city to only allow a certain density, and infrastructure limitations is one of them. I don't know of any big investment in infrastructure for the region, and that what worries me the most.