Pretty interesting that the government is checking garbage trucks for radioactivity and also able to trace t back to a specific business.
This explains why the garbage was checked, and why it was possible to track down the source.
http://www.un.org/esa/dsd/dsd_aofw_ni/ni_pdfs/NationalReport...
Profit is, after all, more important than the environment. The garbage companies in Germany make somewhere between 50 and 100 billion per year.
A plausible explanation would be that the garbage made some fire detectors in a power plant's loading bay to go offline.