The two best options for lab development of your 8X10 film are Borealis in Montréal and Toronto Image Works in Toronto.
Borealis is the only lab in Montreal which offers large format film development. More information on their services is available on their website, but their prices for 8X10 are $10.60 for black & white (and slide) and $10 for colour. They are located at 4600 Ave Hôtel-de-Ville in the Plateau.
Toronto Image Works offers the same development options as Borealis but at cheaper prices. Colour and black & white development is $6 and slide film is $8.90. If you are sending it by mail you will have to pay for return shipping but it could be worth it if you have large quantities of film.