Even if he paid for the house and it was in his name, she could possibly make an unjust enrichment/trust claim for a slice of the pie.
The structure of their relationship is very relevant.
If he paid for the house and supported her or at least paid his share, I would think he has a case to make.
Property Division
Example Cases
Pettkus v Becker - Woman supported man for first 5 years of their common law relationship, so he could save to acquire a bee farm. The bee farm was purchased in his name. Woman then took a major role in running the bee farm. The Supreme Court of Canada decided that man was unjustly enriched, and imposed a constructive trust on half of all his assets, effective at the date of separation.
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Sorochan v Sorochan - During a 42-year common law relationship, woman performed all of the domestic duties, raised the 6 children, and worked long hours on the farm. The Supreme Court of Canada decided that man was unjustly enriched. The court imposed a constructive trust effective the date of separation on 1/3 of the farm, plus awarded a money payment that brought the total value of the award to almost half the value of the farm.
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Peter v Beblow - During a 12-year common law relationship, woman raised children from her previous relationship and from man’s previous relationship. After the first year, she worked outside the home, contributing financially, although never as much as man. She also worked in and around the house, improving it, and gardening. The Supreme Court of Canada found that the man had been unjustly enriched. It calculated the appropriate compensation on the basis of what the man would have had to pay a housekeeper, less the benefit the woman received from the accommodation. As the man did not have sufficient funds to pay this, woman was awarded a constructive trust interest in the entire matrimonial home effective on the date of separation.
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Property Division for Common Law Separation in Ontario[/QUOTE
And to add none of these compare to what the OP posted both parties stayed in the property only a few times. These are talking about time and money contributed and an equal partnership of sorts as far as the success of a lifestyle. The main question was will she need his signature to sell the property and the answer is NO. She could have sold the property before he finds out anything or the courts in Canada could do anything. Or she can just keep it for her and her new "common law relationship"