Most often you'll just be asked to turn off the propane at the tank. Some of the longer eastern tunnels are different as stated.
There are many folks that take their RVs on the ferry from Washington to Alaska - a 3-4 day trip. You just have to plan ahead and finish your food before getting on the ferry or use dry ice for some shorter trips. RV refrigerators/freezer will keep you food o.k. for a couple days with proper planning. Re-purchase small amounts of food when you get to your destination. Don't overload.
Many RVers use the ferries and some tunnels so it's very doable. Many do the Maritimes from island to island. Just read up beforehand so you're not surprised.
You won't have any problem using propane in state or provincial parks. Everyone does.