I think perhaps this is a bogus tape. I mean, the guy meant what he said, but that doesn't mean al-Qaeda is responsible. It could be a ploy on the part of some socialist activists, to undermine Aznar's party.
The dummies used their own cell phones and as usual with these dummies, their ad hoc methods left unexploded bombs with intact cell phones traceable to them. They are islamic jihadis. Whether they are red, or green islamic jihadis doesn't matter. Where ever allah is, there's a bomber.
These idiots claim their god demands all this. It's them. They are the same as muhamed. Just as he conjured up a gang of marauders with a con, to get back at the town that threw him out, so to all his followers from then 'till now. If there's no outsiders to clash wills with, they'll war amongst themselves. It's all about submission, not to god, but to the thug with the biggest sword, or bomb.
I was thinking something similar.