That is yet another very good question. Unfortunately, I'm not very familiar with provincial and territorial legislation on coroners.
It is my understanding that unnatural deaths are brought to the attention of coroners, and then an investigation is undertaken. In terms of whether that process alone would be sufficient to determine whether physician-assisted dying had been provided in a manner that gave Canadians confidence that the person was mentally competent and had been informed of all health care options and was not under coercion or duress, I'm not in a position to say, unfortunately.
It is a very good question, though.