Hmm, yes, there are motorcycle licences in Ontario. I should know, I have one.

What you may be referring to is that the U.K. does not have a motorcycle licence exchange agreement with Ontario. This is true, however, if you get a letter from the authority in the U.K. you can get credit for driving experience and go straight for the full test. This way, you can keep both car and motorcycle.
NB rules may be different, not sure how they work. I'd recommend checking out their website.
Well Ontario does not offer a M/C license when you swap your UK one, you lose the M/C part.
Try looking here
http://www.snb.ca/e/1000/1011e.aspService New Brunswick TeleServices Phone Numbers:
Within North America: 1-888-762-8600 (No Charge Dial)
Outside North America: 1 (506) 684-7901