Ну да, open work permit позволяет, через 6 месяцев работы только...

Open work permit holders (including those in CIC’s Post-Graduation Work Permit Program) may be eligible for Ontario health insurance coverage provided they are employed full-time for an employer in Ontario for a minimum of six months, have a valid work permit during this time, and they:

maintain their primary place of residence in Ontario; and are
physically present in Ontario for at least 153 days in any 12-month period; and are
physically present in Ontario for 153 of the first 183 days immediately after establishing residency in the province.
https://www.health.gov.on.ca/en/public/programs/ohip/ohipfaq_mn.aspx