When is duplicate content not duplicate?

If Google is capable of spotting duplicate content and penalising sites for it how then does it treat online pr websites with likely thousands of multiple duplicate content across other pr websites. Is it giving them some kind of dispensation? I known from research that they apply a dampening filter to links from online pr articles but I wonder how just do they treat the same online article across multiple websites? Do they give it very little value at all if they do not rate duplicated content?