Last time I checked, there were some issues of contention with how the Spanish alphabet should be represented such as c+h vs ch, l vs ll, r vs rr and borrow letters such as k and w not used for Spanish words. If I were to play with a Spanish tileset, which dictionary should I use?
Here's a nice picture of a Spanish tileset that I found: http://gtoal.com/wordgames/details/spanish/
That page links through to the FISE webpages (Federacion Internacional de Scrabble en Espanol), where it is claimed that as of 2009:
El diccionario oficial de Scrabble es la versión 1.0-2003 (edición electrónica) del Diccionario de la lengua española de la Real Academia Española (DRAE).
Hope that helps your investigations!