Usually you will have to convert your licence to JAR, since this is a requirement for airlines flying JAA registered aircraft.
The most likely bet is that you will have to attend to a ATPL theory course and sit the required exams, this depends on experience you have. The course can be done full time in-house or via distance learning. There are various providers throughout Europe. As a Canadian, the UK might be the easiest location for you, although there are some schools in the States that do the JAR course. For starters, see
www.bristol.gs > lincence requirements for more information.