I would imagine that it is. I successfully crossed an umbee with a loiselle so both species can hybridize, it just won't be easy to achieve. To my knowledge that is the only time an umbee had been crossed and documented.
Has anyone seen a Texas X Parrot? My LFS has one that was bred by a local who likes making hybrids. It is pretty, but is only 3 inches or so. It would probably be pretty aggressive right?