Ferret Baudoin, Lead Designer, Obsidian :
"Hrm - my answer to 4 made sense when I typed it, but I could see it being puzzling. The NWN1 prestige classes still don't have spell lists in NWN2. I sort of assumed that in context "in NWN2" is implied. And I know, I know the addage about assumptions."
In all likelyhood, this means that new columns still cannot be added to spells.2da to specify lists for those classes. This also indicates that new spell casting base classes cannot be added in this manner either.