http://www.health.gov.on.ca/en/public/programs/ohip/outofcountry/travellers.aspx
Out of Country Emergency Health Services
Emergency health services are those given in connection with an acute*, unexpected condition, illness, disease or injury that arises outside Canada and requires immediate treatment.
* Treatment for a short period of time in which a patient is treated for a brief but severe episode of an illness, disease, condition or injury.
The Ontario Health Insurance Plan (OHIP) only covers emergency health services at very limited rates. For example, an outpatient visit to a U.S. emergency room may cost thousands of dollars for the duration of your care, however OHIP will only reimburse up to a total of $50.00 CDN per day for this service regardless of the severity of the situation. If you plan to travel outside of Ontario, it is strongly recommended that you obtain additional private medical insurance and fully understand what your policy covers.
For additional information about travelling outside Canada please refer to the ministry's Fact Sheet "Travelling Outside Canada"