I saw a rule that said you can take maneaters as mercs but in order for them to be trusted allies you have to take the ogre captain with them I don't know his name. On page 397 of the core rule book there is an empire army with ogres in it.
I would guess its golgfag's maneaters then from RoR.
If you use alternate allies rules. That's not part of what anyone plays though. If you use the ally chart you can get lots of different army pieces in one army but that's not standard. I don't think I have ever seen anyone play with allies.