Vehicle registration in Quebec is managed by SAAQ, more info here:
Vehicle Registration | SAAQ
Also, you should ask a person directly as I can't seem to find your answer to whether a foreigner can register a bike because you normally would need a Quebec driver's license. Maybe you will need to get an international driver's license beforehand to be able to purchase register a vehicle.
Note that vehicle registration in Canada is a provincial jurisdiction rather than federal. All provinces recognize each others official documents, no problem there, but it is managed at provincial level for your information.
Telephone Information Service for General Information
Monday to Friday, from 8:00 a.m. to 5:00 p.m.
In Québec (city and vicinity): 418 643-7620
In Montréal: 514 873-7620
From elsewhere in Québec, Canada or USA: 1-800-361-7620
** Add "1" in front of 418 and of 514 should you be calling from abroad.
Sales taxes in Quebec are expensive, and so are registration fees because responsibility insurance (no fault system) is incorporated in the registration. Examples: registering an XR650L cost 633 CAD / year, and 377 CAD for a XT250.. speed bikes, hang on tight: 1'425 CAD (considered high risk).
The good thing if you register in Quebec is you can manage registration entirely through the web access, learn the system, use it well. Should be the same in NS. Pls let us know the result of your inquiry. Best!