I got my PR last year on May, and applied for it on Feb 2012. I have been living in Ontario since September 2009 (before PR, I was under study permit).
I got my OHIP coverage on October 2012, and was technically eligible for it from late June 2012 because of the following:
1. As I mentioned, I applied for PR back in Feb 2012, and on late March 2012, I got my email, stating that my application was eligible for processing (we call this email, the PER (positive eligibility review) email
2. Three months from date I got my PER email, I was, technically, eligible for OHIP coverage, but I did not apply, because I didn't know about this, and I kept getting told by others that I would only be eligible for OHIP after I got my medical request (which would not until much later)
3. But around August 2012, I became aware of the rule, and decided to apply anyway, and I got my card around October (similar to other people's experiences, they would initially reject me, then I would ask for them to put in writing, so I could appeal, after which I received a favourable decision)
The point that I'm trying to make here is that, if you are eligible TO APPLY for PR (which is not the same as being eligible for PR), then you are eligible for OHIP coverage. The OHIP brochure even mentioned that passing this eligibility is no longer necessarily associated with getting requested for medicals (you may be eligible for OHIP, even before receiving a request for medicals from the CIC).
For FSW applicants, they usually pass this stage once they receive the PER email (again, getting PER email does not guarantee that you will get PR, only that you are eligible to apply for PR, usually depending upon which MI you're applying under), whereas family sponsorship applicants would probably have to wait until 'approval in principle'.