... the remaining market participants have no such protection from either competition or rampant taxation. It is every man for himself
in the private sector. 

So for example: If an occupant of a property is a small grocery 
store such as on the Danforth it would be easy to predict costs.
Hydro costs are in his records. Wage costs are in his records.
Reported profits are recorded. Wholesale purchases are in his records. It would be quite easy to calculate the effect of property tax increases on his business. Compare his numbers against the 
average for his category and tax property accordingly.

Some competitors would do better others worse. Presumably 
the poorer operators would close up. Rents would determine 
the properties alternate desirability. 

If a jeweller opens up instead of  a beauty parlour simply
tax based on the aggregate metrics for jewellers operating 
in say 2000 square feet. 

Bureaucrats put all that computing power to work or else face a dystopian street scape ...