It's already available commercially though I've only ever seen it for sale here:
http://atlanticajuegos.com/2/spain-in-flames/reglamentos/
My understanding is that the authors sought and gained approval from Battlefront to publish in Spanish. I didn't have anyone's blessing, I just play tested it. I was involved in writing a translation and update of the original
EspaƱa en llamas article for V1 Flames of War (that appeared in the Spanish Times of War magazine some years ago) but I abandoned that when I made contact with the original authors who were producing their own update. At this time I'm not aware of any attempt to translate it into English, nor precisely why this isn't happening.