<...I am wondering if there is any way that the Anthrax spores could be distributed with the bundles of magazines and wind up in supermarkets all over the country.

There would have to be some way to keep the spores dormant or otherwise protected during shipping of the newspapers. Anthrax incubation is 1 to 6 days, and if symptoms started appearing in, well, the mail room, or in trucks, the trick would be detected before the magazines reached their destinations. Do they have those dumb little perfume flaps? I don't read the stuff myself, except in supermarket waiting lines (wait a minute...that's the whole idea, isn't it?)