When I was in Ireland it was optional but I had health insurance. You shouldn't need more than very basic coverage unless you have a chronic health condition or are planning to get pregnant. Most of the GPs in Cork treated med students for free - they had a policy of not charging their own. Also, UCC has a good university health service and again, no charge for visits. The only times I had to pay anything out of pocket was once when I saw a different GP in town and didn't mention that I was a med student. It cost 45 euros and then I had to wait to the end of the year to claim it against my insurance.
The plans do not cover drugs, full stop. Once you have been in Ireland for a year you can apply for a drugs payment card. On this plan you pay the first 90 euros for your meds, then everything after that is free. You don't have to be an Irish citizen to apply for this. You might need a PPS number (it's been a while - the PPS is like an SSN or SIN, and you get it simply by applying for it). It's totally worth looking into if you are asthmatic, as asthma drugs are very expensive in Ireland. There is also a long term illness scheme, again it covers non-Irish people who have been there a year or more, which covers the cost of things like diabetic supplies or if you have CF - it's a fairly short list but again, if you're diabetic, everything is covered. I have asthma, and a sympathetic pharmacist told me about the plan and then advanced me enough meds to get through the summer at home.
I never managed to find Canadian insurance that would cover me abroad; you're out of the country for too long.
The 3 companies that I know of doing health insurance in Ireland are BUPA, Vivas and VHi. Go for the cheapest plan. The details of coverage are often convoluted and confusing, but keep in mind that Ireland has a mixed public and private system, and as a student you are covered by the public system after 1 year in Ireland. The private system is no better than the public, although the hospitals are nicer (or at least, that seemed to be the situation in Cork). I needed an MRI while I was there and got it in about a month, at no cost. I also saw an ENT consultant several times, 3 different neurologists, a cardiologist and an endocrinologist (long story - happy ending), all at no cost to me and all in a fairly short period of time. Cheers,
M