I have never seen nor heard about an Eastern blue tongue cross shingleback. I was under the impression that shinglebacks were fussy breeders and only breed with unrelated individuals of their own species?
There's a pic of one on the bluetongueskinks.net page in the care sheet section ( i think). It actually looks quite nice and i believe it was found in the wild. I'm not condoning cross breeding just saying it does occur in the wild...
Ben