The regular charter operators that snotsicle were referring to, and the majority of operators in canada are, are day vfr only. To operate at night in canada commercially, you need a multi-engine heli. I worked for a company in northern saskatchewan last year and we used to do medevac flights out of reserves for example, all the time, as long as we were day vfr.
There was a company in Quebec, Air Medic, that offered an EMS service with a Dauphin I believe but I think it went T/U a year or so ago. I'm not quite sure why. I have no idea why Quebec has no dedicated EMS provider as does Ontario(Ornge) and Alberta(STARS) but, I can say, that I was watching the news a few days ago and it has sparked some debate about it. How unfortunate someone had to pay the ultimate price before people start to have some interest in an EMS operation.