No and yes. Two factions have the same interests: Eldar and Imperium. They wish to stop chaos, who are playing the orks with misguided information. The orks simply want a weapon, the chaos are the ork's puppeteers, and the eldar don't want this to happen so they ask for help from the imperium. And any other species are in special cases, this includes necrons, tau, dark eldar, tyranids(hope I don't get this one), and any other species that people want(star gods, old ones[unlikely], etc.).

[@Lady Selune]