Although currently living in Calgary, I don't have the answer you're looking for. I will say this is a very common predicament in many regions; namely that data exists for hotels/motels/bnbs but not specifically hostels. So you need to get creative.
Try calling hostels around Canada in various cities. Find out where they got their data when starting (most likely what you've already come across), and how they find the hostel market actually relates to the available numbers. Hostel owners can frequently be pretty open about helping another owner, especially if they aren't in direct competition.
For instance, if you are thinking somewhere middle or East coast and you are talking to hostels in BC, they may be more willing to help. Or even if you are thinking the same province but different region, as you will likely be a feeder city for them (and vice versa). Having a good working relationship helps you both.
Depending on the person and situation they may be willing to be open about their general occupancy, how the seasons run, who their biggest competition is, etc. Start to piece together bits and pieces and it will keep leading you to other avenues to explore. Also depends if you need solid market research for a business plan for a loan, or just to get an idea for yourself. Anecdotal evidence isn't going to go as far with the former.
Consider exploring what is available in certain areas for accommodation- be sure to check not only hotel and motels but also Airbnb & other accommodation sharing websites- and then work to determine if you would be taking part of that market away or working for a different market altogether. For instance, are there lots of young travelers but no hostel, so they end up in motels? Then opening a hostel with competing rates will likely sway them over to what they are used to and prefer. Alternatively, if the destination has more traditional hotel travelers, business travelers, etc. then you will either be competing for them (and need to open a hostel that caters to that crowd) or you will have to market for your ideal client to come to your destination in the first place (quite a bit harder if you are starting small/independently).
Long story short- that data may not exist clearly (though of course keep trying to find out) but there are creative ways to establish a decent amount of info. Good luck!
p.s. I'm not with a hostel in Calgary; just working remotely here right now as a hostel consultant and editor.