5.39. What happens if the sponsor¡Çs common-law or conjugal partner relationship breaks down and the sponsor wants to sponsor a previously separated spouse?
Humanitarian and compassionate consideration may be given, provided the relationship is bona fide and there is evidence that a conjugal relationship has been re-established for a period of at least one-year. In such a case, a marriage certificate is not taken as prima facie proof of a relationship because the marriage had broken down and a common-law relationship had been established.
http://www.cic.gc.ca/manuals-guides/english/op/op02e.pdf