In the last couple of years Montreal's really caught up on the fixed and singlespeed bikes, and I'm surprised it's taken this long for a place like Revolution to open up. Been meaning to hit it.
Not much to add, but yeah, at least 5 years ago Foufounes Electriques (at about 87 Ste-Catherine East) was the couriers spot - punk rock plus the cheapest happy hour in the city. I was there a couple of weeks ago and saw lots of ss and fixed road bikes out front.
They by no mean specialize in them, but ABC on Parc Ave has had Miche cogs, carriers and lockrings in stock, and they're able to order anything Miche or Campy from Marinoni in just a few days. Pierre-Luc has also built up three sets of fixed wheels for me on my own parts (well, and and one of their rims) and they've yet to go out of true even once under a 225 pound 4 season rider.
Also, I noticed that Yeti on St-Laurent now carries Surly frames and Pistas (I nagged them for years on the latter, and now that they have them I've built up my own bikes... sigh) so I'm willing to bet they carry hubs and chain tensioners to go with them.