Mmmm ...
.....
I think the reason that Mcd's 214's are N registered is that there is no type certificate for the 214B in Australia. ...
I don't think that is a requirement any more ... I think (?) legislative changes (EASA?) now allow registration of aircraft based on approved foreign type certification ... and as the Bell 214B has been approved in both Canada and USA that should not be an issue ....
The reality is more like because the machines came from an Ex Mil background (Oman?) some of the bits might not be civillian Kosher ... and thus N reg Restricted category is the go !!
BTW the Bell 214ST has perviously been on the Aus Register as a fully Public Transport Certified aircraft so that is not an issue for that type.