Short answer: no, they are not compatible, you will get double hets.
Long answer: Many expierienced breeders (NERD, VPI/Barkers, TSK, etc) publicly state the three main lines (VPI, Joliff, and SK) are not compatible. I've heard of different pairings from a variety of breeders, and all results were the same: normal looking animals het for Axanthic. Other people with unique lines (such as Markus Jayne) have found definitively that these lines are not compatible from visual x visual pairings and getting all normal looking animals double het for two different lines of axanthic.
Here's the caveat: there are a handful of different "lines" floating around, some may be compatible, or some may be the same "line". But so far, the answer is NOT COMPATIBLE.