Theta Extreme DAC in a Casablanca 1???

Can a Casablanca 1 use an Extreme DAC card? Or is this option only available to the 2 and 3?
The Xtreme DAC came out after the CB2 so I am sure that the Xtreme DAC isn't compatible with the CB1. I've owned a CB, currently CB2 with all Xtreme DACs, for years now.
Yeah but now I'm hearing that it should be backward compatible, which would jive with Thetas policy of upgradability.

Thats from a Theta dealer, and not directly from Theta.