There's a BioShock 2 Multiplayer and Matchmaking Q&A on The Cult of Rapture as 2K Games interrogates itself about plans for multiplayer support for the underwater shooter sequel. They describe how there is no distinction between ranked and unranked gameplay, discuss dealing with griefers, and outline systems that will allow you to stay buddied up with a group of friends. They also explain that the game will not support dedicated servers or LAN, saying this is due to time considerations:

Do you support LAN play on consoles or PC? Do you support dedicated servers?
Short answer, no and no. There is always a finite amount of time for the development of a game. Bringing Multiplayer to BioShock was a daunting task between the tech (there was no multiplayer support in the codebase from the first game) and the expectations of the community. Either you try to do everything and so nothing feels finished or you focus your efforts to do a smaller number of things really well like an accessible online experience. We chose to spend the time we had creating a solid game foundation and unfortunately that did not include LAN play or dedicated servers.