A few weeks ago, I saw something about another Spanish mvno with cheap int'l calls, but was busy and forgot to look again, and now I couldn't remember the name ...
I found 5 new ones, not all launched yet, Viva, XL, fonyou, Masmovil, Hitsmobile, the last two with cheap int'l calls. There are connection fees of course; the off-peak rates to foreign mobiles might be worthwhile
http://www.masmovil.es/MasVidaMovilSelfcare/es/201.html
http://www.hitsmobile.es/web/en/tarifas/internacionales