In addition to a nearly three-minute video interview with World of Warcraft: Cataclysm lead systems designer Greg Street on G4, there's a preview of the Tol Barad PvP zone up on the official website. From the latter:
Similar to Wintergrasp, Tol Barad will serve as an open world PvP zone, although there is also a hub on Tol Barad Peninsula for both factions to complete daily quests. Reachable by portals in Stormwind and Orgrimmar, or via a level-85 mage teleport or portal, Tol Barad will accept up to 80 players per faction to engage in brutal combat across the island's surface. Unlike Wintergrasp, Tol Barad will not have Tenacity buffs. Instead, the queue system will attempt to match each side at a 1-to-1 ratio. Battles will take place every two hours and thirty minutes, giving the offensive faction a chance to claim territory.
Tol Barad will feature capture-point gameplay. There are three keeps and three towers for the defending side to hold. When destroyed by the attackers, each tower will add five minutes to the standard fifteen-minute battle timer. In order to win, though, all three keeps must be captured and controlled by the attackers. If these keeps cannot be taken by the attacking forces, the defending faction will claim victory in Tol Barad. Similar to Eye of the Storm, Tol Barad determines whether a keep has been captured by the number of players from each side in the immediate area. There is, however, a new twist: each time a member of your faction is killed in the immediate vicinity of a keep, a slider bar will move slightly in favor of the opposing faction. So not only does the size of each force in the area determine who controls each keep, but losing allies during the contesting process determines control as well.
In order to destroy the defenders' towers, attackers will have access to an all-new type of war machine: Abandoned Siege Engines. Six of these Siege Engines will be placed around the map, and these vehicles can be used to bombard the towers. In contrast to the Siege Engines of Wintergrasp, these machines cannot attack players or buildings while the vehicles are being driven. Instead, players must drive them within range of a tower and jump out, allowing the vehicle to transform into an automated cannon that can lay siege to the tower. The Abandoned Siege Engine will continue to damage the closest tower in range until the machine is destroyed by opposing forces.