There is more to this story...
Still to be determined if true but sources say that the reason the aircraft was still "American registered" was it could not meet the technical requirements to be a "Canadian" registered MU-2.
Also at first it was mentioned that the aircraft was chartered which would have been illegal with an "N" tail in Canada but it now seems the owner of the aircraft which may have been one of the pilots onboard was a friend of M. Lapierre and to help him get to his dad's funeral decided to fly him and his party into the island.
The reason this came about was that Air Canada/Jazz had apparently cancelled their flights into the island because of the bad weather which incidentally got worse after the crash... Very sad story.