Alliance Points will be tied to the PvP ranking system. Siege weapons can be obtained and created by anyone who has enough Alliance Points to purchase them; there are no other resources necessary to buy and deploy them. Players can effectively starve out an enemy area by depriving them of resources from surrounding lumber mills, farms, and mines. Seizing those resources before laying siege has a double advantage of also switching off various enemy patrols. Villages in Cyrodiil are Alliance-neutral, but if you control nearby keeps, you'll have NPC patrols in their surrounding villages and towns.
The team isn't quite ready to talk about some features like territory ownership perks and large team sizes. You can delve into full detail over on the official post.