Hi Tim,
The OWA doesn't provide soil testing.
There are many soil testing labs in Ontario. A few include A & L Canada, SGS and the University of Guelph Agriculture and Food Lab.
https://alcanada.com/agricultural-testing-diagnostic-services/soil-analysis/
https://www.sgs.com/en-ca/industry/agriculture-and-forestry
https://afl.uoguelph.ca/our-services/plant-soil-health-diagnostics/#SoilandNutrient
Costs will depend on a variety of factors such as the quantity and metrics being tested.
You may also be interested in a few recent articles in The Ontario Woodlander about soil. Take a look at issue 113 pg. 20 and issue 115 pg. 54.