I recall a very few times in Ontario when RCC assisted with an inland/GSAR incident. Typically, it was when hoisting was required. OPP helicopters aren't equipped or certified for hoisting and I'm not aware of any civilian assets that are. As I recall. the response was much faster than the traditional 'aid of the civil power' route but I don't know the mechanism or channels.
The reality is the high incident areas imply population density and positioning emergency assets further away would politically unpalatable and possibly seen as a liability risk. It could also raise costs since multiple responses from further away would be more costly.
It is also a matter of jurisdiction. As pointed out, federal and provincial responsibilities differ.
Expensive and highly specialized assets simply can't be everywhere. It might be nice to have a SAR base in Iqaluit but they will be sitting on the hands getting rusty while the world moves around them.