I think these flights make perfect sense for AC. After MX left *, RG was the only * carrier with service to BOG, and GRU is hardly on the way between BOG and Europe or Asia.

Avoiding U.S. customs and immigration is a big plus on these flights. Even for people who need transit visas for Canada (like Colombians do), they're a lot easier to come by than U.S. transit visas. Canadian transit visas are free (vs. US$100 for U.S. transit visas), and can often be obtained by mail (vs. making appointments for a visa interview months in advance, and then traveling to the U.S. embassy to get a simple international-to-international transit visa). Another advantage: On international-to-international transit through Canada, you don't have to reclaim your luggage and bring it through customs, unlike when transiting the U.S.

And YYZ is not as far out of the way as it might seem, even between Europe and BOG. For example, LHR-MIA-BOG is 5930 miles, while LHR-YYZ-BOG is 6260 miles. That is a difference of just 330 miles.