From the linked article: "... the Vatican often extends authority to absolve certain sins and to lift excommunications at big papal events." There is no "new light" involved, only procedural adjustment to meet a temporary need.
Lifting excommunication is normally the purview of the local bishop, but they are empowered to delegate that function to other priests of their diocese. The special situation in Madrid is that other clergy, who are not under authority of the Madrid diocese, will be on duty during World Youth Day. Considering the size of the crowds at that event, the local bishop and priests couldn't possibly meet the demand so they're having visiting clergy help out. That's a very brief summary; read more about this on Fr. Z's blog (about one page down) if you're interested.