Someone else might be better to chime in on this, but I have seen a few crosses like that, from time to time. In my short course of studies, I have learned that some irises are more fertile than others.
As far as what doesn't cross would be beardless irises with bearded.
Some arils will cross, with bearded, each having varying degrees of fertility. I am going to try to cross some arilbreds with bearded. I don't even know if they will take. Some seeds take up to 10 years to germinate! I don't know if I will live that long.
