The domain name BU.ca has reportedly sold for $13,500 CAN at domain drop catcher Pool.com
This domain name expired and was snapped up by Pool, one of a number of businesses that 'catch' expired domains and auction them off to the highest bidder.
The previous owner of BU.ca either forgot to renew it, or purposely let it expire because they didn't want it anymore. Once a .ca domain name expires, it goes into a 30 day suspension period where the previous owner can still renew it. If they don't, it is released back and becomes available to anyone. Highly desired names like this usually get registered within seconds of becoming available.
The acronym BU could be used for a website about Bishops University, or Brandon University, or a subject to do with Business.