Ogres are notorious mercenaries, indeed much of their culture revolves around fighting in exchange for wargear, gold or even huge quantities of meat. Several Ogre units may be used as Dogs of War in other Warhammer armies. If the entry for a given Ogre unit type has the special rule 'Dogs of War', they may be taken in a Warhammer army with the option of taking Dogs of War as a Rare choice. Maneater units are rare even in the ranks of the mercenary world and hence take up two Rare slots instead of the usual one.

In a Dogs of War army, any Ogre unit with the Dogs of War rule counts as a Special choice.
Similarly, Ogre armies are not above fighting alongside other Dogs of War units, and hence may employ Dogs of War themselves as Rare choices. Note this cannot include troops from the Ogres list itself. Ogres are unlikely to pay money for little thinlings and their like to bolster their ranks, this kind of alliance can be put down to a common cause. It really doesn't take more than a couple of stomach rumbles to get an Ogre up and fighting, after all...