Well here in calgary (not that far from you) we get a referral sheet from the doctor and on the side of it, it has a list of numbers and locations on it. At the very top of the sheet it has a central number where you can call to get an appointment asap or you can call a specific location and see when they can get you in next. I am not sure if you guys are the same as us, but that's how I do it. If the referral sheet doesn't have anything on it, you can always ask your doctor for a list of locations that he reccomends.
Oh and the hospitals here do have ultrasound clinics but I amnot sure how they work and if you can just take your referral to them and book an appointment. You can always call your nearest hospital and check though.