4everchan's link tells you all about the berries, which are widely grown, just happen to have the same name as the city. They look like blueberries but taste, to me at least, tarter, more like cranberries. My mother just used a blueberry pie recipe and substituted Saskatoon berries.
You can buy the jam on Amazon.ca or in many grocery stores. I've never seen the berries growing wild, but my husband often brought home a tin of them when he'd been backpacking in the mountains. He'd let me have some to bake into muffins, and he'd dry the rest for his homemade trail mix.