Cogeco (Ont) will allow you to use an outside STB so long as it is supported on their network. Cogeco (Que) will only allow you to use a unit already authorized in their system.
Eastlink will allow you to use an outside STB so long as it is supported on their network. Eastlink does share common databases with several other major US providers, and will not activate a unit if it appears in one of those databases.