You don't need to speak french to work in Tech in Montreal, but you won't be able to work everywhere. I know many people who don't speak french and work in mtl.
Montreal is probably the only city in the province where you don't need to speak french though.
They're only a bit worse than Toronto winters, and Toronto is attracting lots of tech from the States. It's not the main problem. Though I guess people who tolerate very cold weather climates may not correlate much with people who enjoy French as the main local language?
I don't know for sure either way - I only arrived at the end of February, and last winter was unusually intense and long in both Montreal and the northeast US where I was just before.
Still, if it is just 4 months, that's pretty close to canonical season length!
They offer lots of coping mechanisms too like the underground city in the downtown core and good home heating, plus lots of outdoor and indoor activities to make the winter enjoyable.
1. You need to speak French
2. Winter is brutal (forecast for next 10 days, and it's only October: https://weather.com/weather/tenday/l/CAXX0301:1:CA)