I've always believed Caldera is Hlaalu because of the Ebony Mine situation. Although the Redorans thought they should have been granted the deeds, Hlaalu sneaked in and got them instead. The predominant power base in Caldera then became Hlaalu, or at the least had more connections with Hlaalu than anyone else.
QUOTE(paragenic @ May 7 2008, 07:43 AM)

Don't tell me you think Ebonheart is Hlaalu too because Duke Vedam Dren is there...?
No, that's just you being facetious. Ebonheart is Imperial, and doesn't seem to have leanings to one of the Great House over any other.