As you've said, if it's unlocked, I don't see why it wouldn't work. I tried doing some searching for you regarding to supported LTE bands on the iPhone and the bands used in Canada, but I didn't come up with much information.
Thanks! Unfortunately, once you mentioned LTE bands, I decided to look into that (I'm a newb when it comes to smart phones) and found my phone model's LTE is only compatible in Japan and USA (https://www.apple.com/iphone/LTE/, my model is A1453.) How much of a problem would not having LTE be if I try to use the phone in Canada? I wouldn't be doing anything heavy duty with it - mostly messaging or checking Facebook.
no reason why it shouldnt work in Canada. I connect via vpn to their servers everytime from Japan, and have never had a problem with it. Unless your phone is locked to a network in Japan. I would strongly advise you unlock it before travelling to Canada