All I can personally say is that I didn't pay any extra fees for the original game when I got it. I also got the signed copy so my box probably had to pass through the US originally. Additionally, I don't remember anyone on the forums complaining about paying extra customs fees, but my memory may be faulty on that.
I also assume that, at this point, unless Obsidian is certain the same company(ies?) will be used for international deliveries, how international shipping will be handled isn't set in stone yet, so Obsidian might not have a definite answer to give yet.
I'm a volunteer mod by the way.
Edit: Forgot about Paradox. Paradox is the publisher, and they're based in Sweden so there shouldn't be any reason for you to pay extra fees if you are within the EU.