Great buns - Calgary
I am mad for Eclaire De Lune's Pain du lait - order ahead - I know that "technically" it's not as appropriate as other buns, but it's the only bun in town that fulfills that white, slightly sweet flavour that echoes childhood hotdog buns. I use them for braised lamb / smoked chicken / BLT's / brisket sandwichs all the time. Pure Brilliance.
I've served beef on a bun for a crowd and find Costco's ciabatta buns are great. They don't get soggy (crispy exterior) Plus the buns are smaller than your average hamburger bun, which a lot of people like, especially if it's a buffet situation.
If you're looking for a bigger bun, Safeway sells pretty decent french bread rolls that are about 5 inches long, which I've used too.