my husband called OHIP a couple weeks ago and asked about this very topic. The person he spoke to at OHIP said you would be covered for emergency treatment in the US up to 7 months or until you obtain PR status in the US.
My argument was you should be covered until you obtain CR/LPR status since you arent considered as having abandoned your residency in Canada until the US says you're legally allowed to do so. If your AOS or CR-1 were to be denied , you would have no choice but to return to Canada, so technically I would think you'd be considered a visitor until that time.
A PHP requires you to be a resident of the province UNLESS you're going to be out of Canada temporarily......
the temporary absences are;
study
work
missionary work
vacation/other
......and its the "other" that has me wondering
NOW......OHIP says "Ministry of Health and Long-Term Care may continue your eligibility for Ontario health (OHIP) coverage when you are absent from Ontario for more than 212 days in a 12 month period, as long as you plan to return and make your permanent and principal home in Ontario."
http://www.health.gov.on.ca/english/public...hip/longer.html