Sounds like a usual GPS receiver thing - there's no reception on the ferry car deck, so when you drive off the ferry the GPS receiver needs to re-acquire the satellites. Which is usually quick unless your position has changed significantly since when you last had signal. And I'm guessing you were on the ferry for a couple of hours, so yes, it's going to have trouble re-acquiring the satellites. Be patient and it will come back. Of course that's not much help when you're trying to figure out how to get from the ferry to where you want to go ...
But to answer your questions, yes, you can see the map of Canada in Canada.
I've been in Canada for 2 weeks and it's been working great! Hopefully it's just the ferry issue mentioned above.
The automatic integration of km/h measurements and cruise control upon border crossing with concurrent mph display while retaining mi in navigation system is well thought out.
I have crossed at land borders to and from the US a couple of times. The vehicle will automatically start showing the KM vs M etc as soon as GPS picks up you have crossed.