I think Al Qaeda will put thier hands up to anything...they even claimed to have caused the NY blackout recently...
its interesting that no one has officially owned up to the bombing but if it was ETA, then i believe they would of had help in the materials and organisation...possibly from Al Qaeda because they have been planning a european terror campaign for some time and although security is tight in Spain, an insider (ETA) may be a good 'way in' for them
thing is, now NY had its hit, then Madrid,....who was the other major ally of the US?....is London next on the terror list?