I would suggest that it's not banned under E's rules. I think bestiality (note the spelling) concerns dumb animals who cannot think and have no say about what's done to them. Furries are essentially self-aware fully cognizant intelligent characters RPed like any other non-human character (angel, demon, succubus, tentacled alien and so on), its just the skin covering that is different and that they may be based on earth animals like wolves, unicorns, etc and so in my mind it would be fine to have these.
I consider neko play to fall into this category.
I think even if a full animal is RPed as having intelligence and free will it wouldn't be bestiality, though my understanding is E's rules do not permit pictures showing sex between humans and animals in such games.