The protozoa that causes coccidiosis can be found just about everywhere. It only seems to become a problem in rabbits when the rabbit is under stress or when the parasite load becomes extreme. Pin worms likewise are very common. Either of these things could be caught by feeding greens contaminated by wild rabbits. My understanding is that these organisms are species specific (that is, rabbit coccidosis affects only rabbits, not chickens or goats; and rabbit pin worms are not the same as dog or cat pin worms.) So yes, there is some risk feeding greens, but unless you are overrun with wild rabbits and/or live in an area where these problems are out of control, it is a small risk. Washing the greens before feeding them may help minimize the risk... not sure how effective it would be.
Neither pin worms (which are only in the intestinal tract) nor coccidiosis affects the quality of the meat, but in the case of liver coccidiosis ("spotty livers") the liver itself is considered unfit for consumption and should be discarded.