an older bunny can definitely be littertrained, but how old are we talking? i know some vets will not neuter past 2 or 3 years old. on rare occasions even neutered males will spray. therefore, i can’t give you an absolute answer b/c it is going to depend on him. and i wonder how having unspayed females in the next room would affect him…?
edited: i was looking around a bit more for some info.
source: http://www.veterinarypartner.com/Content.plx
Prevention of Urine Spraying – Both male and female rabbits can spray urine on vertical surfaces to mark their territory. Intact mature males do this at least 10 times more frequently than females. In addition, the urine from a sexually mature male rabbit can have a very strong odor that is unpleasant to many humans. If this behavior is allowed to continue for a long period of time, it may be impossible to completely stop this behavior. Therefore, it is best to “nip it in the bud” and get the little guys neutered just prior to shortly after sexual maturity.
did she say that he does spray a lot right now?