I think they can. I have an AR movie Arceus (the one that came out in Japan) on my Platinum and it activated the in-game event with the history of Sinnoh with the one hiker. So with that logic I would think yes (though this is just a guess as it is hacked, and not one hundred percent completely verified.)
Cactuar wrote:
Say Nintendo has that Arceus event in America, and i trade it to my JP HeartGold, would I be able to get a Dialga/Palkia/Giratina egg?
They aren't eggs. You just encounter them at level one, like Regigigas in Platinum.