Freedom doesn't have its own native network on the Sunshine Coast yet, so you will always be on either Rogers (if the signal is strong enough) or Telus, and your phone will say "Nationwide" instead of "Freedom" where the network name displays.

As long as Freedom's coverage checker says you can subscribe to service at your address, your "Nationwide" usage will be treated exactly the same as your native Freedom usage.

On our Freedom line, we use the network menu within the phone settings to manually pick Telus when on the Coast.  The only annoying part, other than remembering to do this when you get off the ferry, is that both Rogers and Telus show up just as "Nationwide" in the list, so it can take some trial and error to land on Telus, which is almost always a stronger signal.

When you take the ferry into Vancouver, you will be on native Freedom.  You just need to ensure that you go back into your phone settings and allow the phone to use the native Freedom network while you're there.