Upvote:3
Yes, someone on a transit visa can leave the airport -- some people transit between different airports, or between airplanes and another mode of transportation, which will definitely require leaving the airport.
Note that usually when someone does an international-to-US transfer in Toronto or Vancouver during business hours, leaving during the same day, you go directly to the US preclearance, without going through Canadian border controls first. Once you go through US preclearance, if you want to change your mind and go back out, you will need to go through Canadian border control again.
However, in your case, the length of the layover means you will be leaving the next day, I believe you cannot go to US preclearance immediately, and will have to go through Canadian border controls first anyway. And since you will have entered Canada, you are free to leave the airport if you want.