Cats can excrete the toxoplasmosis parasite. That's the reason pregnant women aren't supposed to have contact with cat litter--the parasite is harmful to human babies, but not human adults. Toxoplasmosis is very harmful to rabbits, however, so I would be very careful about allowing rabbits to spend time around cat litterboxes. It is rapidly fatal to rabbits. If you are sure your cats do not eat rodents (where the cats get the toxoplasmosis parasite), then it should be safe.
Cat bites and scratches are also a big worry for bunnies. They carry a lot of bacteria in their mouth and on their paws, and a cat bite can also be rapidly fatal for a rabbit.
So, cats and rabbits can get along, depending on the behavior/personalities of all creatures involved, and if you're sure there will be no biting or scratching of bunny and if you're sure the cat doesn't carry toxoplasmosis from eating mice, etc.