TL;DR Most butchers I saw were unsure where the beef was from, or if/how it had been aged. Marchand du bourg is an exception - that fellow knows his beef. If he doesn't have what you want, the sheer number of butchers at Atwater market should make that your second place to visit.
Since this is becoming the de facto Montreal steak thread, I'd like share my recent shopping experiences here.
I moved to Montreal in 2011 from the GTA, where I had access to three great shops (Angus, Cumbraes, and Whole Foods). I got used to having access to dry-aged striploin, cuts to order, knowing where the beef was from, and only rarely having the feeling that I was being lied to just to make a sale.
In Montreal, sadly, this is not the case. Clerks don't seem to know where the beef is from, how it was aged, and seem to make up an answer and pass it along as fact (see below about my experience at Claude et Henri).
How we cook steak:
Blue. In brief, let it rest for 1-2 hours at room temp, pat dry, cook 1-2 minute a side on cast iron, sear the edges for a few seconds, let it rest for 1-2 minutes in a 325F oven, then eat. No seasonings/oil.
These butchers all have a wide variety of cuts, but I only write about the steaks I really looked at or bought at that particular store.
Boucherie de Paris (Atwater Market)
What caught my eye: Onglet, and their pre-cut steaks looked dry (not dry aged per se, but that dryish look that steaks patted with paper towel get)
Prices: $20/kg for Onglet
How was it: Although we bought one, it's still in the fridge...
Fermes St-Vincent (Atwater Market)
What caught my eye: High prices, and (believable) claims of local biological 'Charlevoix' beef, I got the sense this is a boutique butcher dealing in local meat.
Prices: Over $60/kg for filet and rib.
How was it: I'm not rich enough to buy any. Would love to know someone else's impressions.
Boucherie 2 Freres (Atwater Market)
What caught my eye: Dry-aged loin and rib, with a nice dark exterior. The steaks are cut on request.
Prices: $45/kg for filet. Forgot the price of the loin/rib.
Where's the beef from: They claim the beef comes from Quebec
How was it: The filet we had was extremely tender, decently marbled, perfectly trimmed, and tasty. A bit light on flavour (even for filet).
Claude et Henri (Atwater Market)
What caught my eye: The marbling on a few of their steaks (most were marbled like Canada AA/AAA, but a few more like Canada Prime to me).
Prices: $45/kg for filet, $26/kg for T-bone
Where's the beef from: They claim the beef comes from Alberta, although that took some doing to figure out.
How was it: The filet mignon was very good, and checked off all the major boxes: tender, flavourful, well trimmed. The T-bone was a mixed bag. I actually trimmed it and separated the bone before cooking - what started as 590 gr was trimmed to 410 gr. The strip loin side was sinewy in places, and amazing in others. The tenderloin side was outstanding throughout, even more flavourful than the filet mignon I have bought separately. It was thin, which made it tougher to cook blue.
The first clerk I talked to told me that his beef came from Quebec, and was all dry aged. Certainly, some of the T-bones and rib steaks in the display case appeared dry aged (darker meat on the edges) but not all of the meat had that 'look'. Since I have been looking for dry-aged sirloin for some time, I asked him for one steak. Not having any in the display case, he went to the back and brought out a cryovac'd sirloin… full of purge. He told me that they dry-age the steak and then put it in the cryovac bags - something that I don't quite believe given the degree of purge in the bag.
Later on, I spoke with a clerk who was much older (50s or so) and if not one of the owners, certainly a manager who would know a bit more. He told me their beef certainly comes from Alberta. I bought a filet mignon and a T-bone from the display case (about 3/4 inch thick). The T-bone looked aged and was well marbled. Judging from the size of the tenderloin side (and the sinew in the strip loin side) it was most likely one of the first cut steaks (i.e. closer to a porterhouse).
Belanger (Atwater Market)
What caught my eye: How incredibly red their steaks looked, like they were dyed!
Prices: around average ($45/kg for filet, I think)
Where's the beef from: The clerk didn't know.
How was it: No idea, because I bought nothing. Between the way their steaks looked and the lack of knowledge by the clerk I didn't give this store a second thought.
Boucherie AGA (St-Leonard)
What caught my eye: They have 4 whole rib subprimals sitting in the fridge, with varying degrees of marbling (one looked like Canada Prime to me), which they cut to order.
Prices: $45/kg for filet, $33/kg for strip, $30/kg for rib
Where's the beef from: The clerk was not entirely sure where the beef was from, and it was busy enough that I didn't press the issue.
How was it: We bought a 20 oz boneless rib steak (sadly, not the uber-marbled steak). Cooked very well, was tender, and easy to cut. However it was rather bland. We both found it blander than a tenderloin, even the 'outside' of the rib steak. Disappointing, but I will go back to try once more.
Boucherie le Marchand du bourg (Beaubien/Papineau)
What caught my eye: Where to start. The store itself, the walk-in cooler, the aged steak.
Prices: $31/kg for unaged strip, $45/kg for 40-day dry aged bone-in strip, $60/kg for 40-day dry aged bone-in rib, $24/kg for bavette.
Where's the beef from: Alberta
How was it: I bought a strip loin, but since he had been closed for three weeks prior, it was aged 21 days or so. Normally they don't have dry-aged strip. I did trim it a bit more (there were a couple of spots of mouldy fat on the edge, and I'm paranoid). It cooked beautifully, with good browning on the outside. The texture was very good, not chewy at all. There was a slightly nutty taste to the meat, moreso in the outside edges. I've never tasted that before in a steak - I'm still not sure whether I liked it or not (but I'm glad I tried it!).
In closing, I've still not found the dry-aged striploin that started me on this beef-hunt. If anyone knows of a good place, please let me know!