As far as I am aware, the Mosaic Cal King is not related to the Mosaic Florida King. I'm not so sure it's really a co-dom trait, however. Perhaps some lines may be, but the ones I have don't seem to be.
I only get one or two Mosaics from both of my Mosaic female's eggs combined each year. I do get the usual somewhat unpredictable variability that ranges from the patterns of each parent. I will be breeding a Mosaic to a Mosaic in 2012, so we shall see if I get a clutch of "super" forms... though I doubt it.
Regardless, this pattern variation is one of my favorites, and one you don't see really good examples of too often.
As far as their origin, I'm at a loss. I really don't know who started breeding for the pattern.