Essentially, most schools don't take too kindly to attending two different universities at the same time. I think they might even kick you out if you try to, or at the least, deny you transfer credit.
So, you attend one school, and get that school to give you a "Letter of Permission" to take a course at the other school. Unfortunately, they'll usually charge a small sum of money for this (mine charged $25 per letter). By doing so, you'll pay the other school's tuition, and they don't discriminate based on what program/school you're coming from, but the school I took the course at on a LoP charged me an LoP fee of $75.
I'm not sure if your school would give you a LoP to take a course during the school year, but they likely would over the summer (but I make no guarantees).
So, benefits:
1. Lower cost (if they let you)
2. Spread out your academic term over the summer (easier load)
3. (Potentially) easier courses
University of Western Ontario, University of Waterloo and Athabasca Open University are 3 that I know of that have rather extensive distance study offerings, and extensive testing centre availability.