In Ontario (as with most places in North America), commercial property is assessed on its highest and best use (ie potential use), not its current use. So if a parcel has a low-rise building with some bookstores and cafes, it will be assessed at the same value as the high-rise condo tower next door.
This "highest and best" assessment rule means that in a rising market, the landlord must raise rents to cover rising property taxes. In addition, a landlord may apply for a property tax rebate if a commercial or industrial property is vacant.
So there is zero incentive for landlords to accept below-market rents for small businesses: if the property is vacant, they don't pay property taxes. If the property is rented at below-market rates, they lose money because they still have to pay property taxes at full-market rates.
Even if the small business owner also owns the building, the rising property taxes may make the small business uneconomic and force them to move.