The reality is there are no "deals" on domestic airfare in Canada. When they pop up somewhere, they are generally smoke and mirrors. The fares are what is publicly available from the airlines, and so is the availability.

There are sometimes deals on international travel via consolidator fares (depends a lot on destination), but at least in my experience they are generally available in ethnically-focused travel agencies, not easily findable on the internet.

Where Google Flights, or its engine under the hood, ITA Matrix, help, is that they are better than airline websites and the major OTAs at ferreting out how to mix and match fares with different pricing points and/or across different airlines. Recently, for instance, I booked a trip YOW-FCO-PRG-MRS-YOW. ITA Matrix helped me find that YOW-PRG was cheaper than YOW-FCO and allowed a free stopover in FCO. PRG-YOW didn't allow a stopover in MRS but PRG-MRS was not expensive on another airline, and YOW-(PRG)-FCO and MRS-YOW can be paired as an open-jaw return. The Air Canada website, as well as Expedia, would choke on this in many ways.