There are different car seat laws in Canada vs the US with regards to acceptable seats. However, as bcwife76 indicates, I do believe that "tourists" are allowed to use the safety equipment they own (similar for Canadians coming to the U.S.). The point of the exception for tourists is so every tourist entering another country temporarily doesn't have to stop at the nearest store to buy a new car seat. Since the BubbleBum is considered an "extra" packable seat to use for travel purposes, it may or may not pass the "tourist" exception. As mentioned, if you are traveling by car into Canada with a child already sitting on it, it may be fine; bringing it for sole purpose to use in a taxi might not be allwoed.
Enjoy your cruise!