The rent CPI is a downward-biased measure of inflation and has been for a long time. A 2016 study by Head et al in the CJE suggested the bias could be as much as 0.8 percentage points per annum, for the country as a whole. Poloz should be complaining to StatCan that they have to fix this, and a lot of other problems with the CPI,  but he is a go-along-to-get-along type of central banker, so it isn't going to happen.