I've found two threats and a warning to the Spanish government by the Spanish police, prior to the train attacks. The police warning may be referencing intelligence rather than a notice.
A new threat video was being recorded when the Spanish police were kicking the goblin's door down, according to a review of the tape. There was also another warning letter after the trains were attacked.
It appears that there are no rules whatsoever.
Thanks, that has been my thought too. You lose your advantage if you telegraph you timeline, suprise is an important component of combat. I have similar concerns regarding islamic numerology and cosmology (sp) and attack dates. Something I'm trying to research further.