I don't know whether you know siege vehicles of Wrath of the Lich King or not, this is a particularly interesting addition to world of warcraft's PvP system. Coming to World of Warcraft as part of the Wrath of the Lich King expansion, siege vehicles are capable of razing buildings similar to killing an Alterac Valley commander.
Siege vehicles in World of Warcraft, Wrath of the Lich King will be pilotable by players and look to be quite powerful. Unfortunately, their use is limited to the Lake Wintergrasp and Northrend Battleground zones. Currently, none of them can travel through water. Different races have different siege vehicles, but they can be used by any race. They are not owned like a mount or used as an inventory item like any World of Warcraft mount. They are all relatively slow as far as travel speed, and some can carry more than one player. These siege vehicles definitely look like they will have a significant impact on World of Warcraft's Player vs. Player (PvP) combat.
Demolisher
This is the baseline vehicle which has both short and long-range attacks and a ram attack. The vehicle can also carry up to 3 passengers as well as a driver. In this vehicle the passengers are exposed, allowing them to be targeted and attacked -- but also allowing them to do the same. The driver is also in control of both weapons.
Siege Engine
Siege engine is The hardest hitting and longest range vehicle of all, it carries a driver, gunner, and passengers. Unlike the Demolisher, the passengers are not exposed. The driver controls only a frontal ram attack, while the gunner is control of a fully mobile turret.
Bomber
A flying vehicle bomber variant that was not shown at WWI. It was only mentioned that it will carry both a bomber and pilot, allowing it to drop bombs over the battlefield.
How to obtaining them? This seems to be an unrevealed question till now. However the design goal is to make them exciting and the rush to obtain them fast paced and frenetic. Some fans have complained that these vehicles do not look "cool enough", but they seem to fit World of Warcraft's visual style as far as I can see from these early concept pictures.
Source: www.wowruler.com