At least initially, it appears the yeast in question was WLP570 (Belgian Golden Ale Yeast). I can't find a direct confession from Stone, but that's what seems to add up from these two sources.
First, from Craft of Stone, pg. 78...
"When we set out to make the Stone 08.08.08 Vertical Epic Ale, we wanted it to have a very light color--so light that we thought the residual Stone Pale Ale mixed in with the yeast would darken the brew too much. So we opted to grow the yeast in Stone IPA wort. After separating out the yeast and transferring it to the tanks for the Vertical Epic Ale, we tasted the resulting Belgian-ized Stone IPA and were inspired to dry hop it with Chinook hops, as opposed to the Centennial we use for Stone IPA. The result? Stone Cali-Belgique IPA."
And so the recipe notes for Vertical Epic 08.08.08 at http://www.stonebrew.com/epic/Wca256c660276b.htm
White Labs WLP 570 (Belgian Golden Ale Yeast)
This is the first time we’d really used this yeast. It’s a good strong fermenter, produces a lot of phenolic and clove character, and doesn’t flocculate worth a damn. It was a bear trying to filter this beer. Feel free to use another Belgian strain if you want your beer to be more clear, but we liked the flavors that this strain produced!"