I can be wrong about the landing in Asturias, because these operations are not very known and I haven´t enough information. But would the Italian had disembarked in Barcelona?
I have also read that these operations were planned to counteract an allied invasion, but there were several reasons to invade Spain for the germans (Gibraltar, the change of the Spanish Policy,...)
Besides, there were four operations for this invasion, weren't?
Operation Isabella (1941) - A full scale invasion.
Operation Ilona (May 1942)
Operation Gisella (September 1942)
Operation Nurnberg (1943)
About Isabella there is a web that explains something
But I´m not very sure of some facts Did the Goliaths exist in 1941?
Bye and Regards from Spain