From what I remeber, it is a PITA for the licencing of the car. A
couple of guys I used to work with (who ere from Montreal and
worked in Ottawa) did it. You have to get temporary permits etc.
It was a hassle. I doubt that Montreal dealers are going to give
a significantly better price but it is always worth trying.
A lot of Ottawa people like Lachute Subaru-Suzuki for their service
but I don't think anyone has posted on buying there. They are
close enough to Hawkesbury that they could licence a car directly
in Ontario an save some hassle.