There is no inheritance tax in canada. But goverment would tax the capital gain tax upon your death. The principle resident (the house you lived in) is exempted from this tax. So this mother could leave her house to her son without any tax.
The reason you should never put your kid on you principle resident.
1) If they are in bankruptcy , the bank can't get your house.
2) If they divorce, their ex-spouse couldn't get your house.
3) If they get sued(like injure someone in a car accident), they wouldn't get your house
4) Besause you keep your house safe when your kid in trouble, They still have a house to move back in.