While I'm not aware of CA having specifically said so yet, they have obliquely indicated that diplomatic relations will be set to neutral (amongst all factions) at the beginning of the game. Apparently this is being done so as to give the player greater flexibility in recreating history as they wish.

That said, it's also been hinted that at least some factions will have a greater natural antipathy for certain nations. So I don't think we have to worry too much about England cozying up to France, or Sweden becoming best friends with Austria and Russia, etc.