Research into muons has been ongoing since the 1950s. Your cite says absolutely nothing new. They only published it as a popular science article because of damaged medical cesium shipment in Australia, it is NOT a research report.
The actual incident was about a rather small lost caesium-137 radioactive source, that had fallen out of its shielded housing in transit.
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It was so intensely radioactive that it was easy to find - the radiation detector that found it was travelling at 43 miles an hours as it drove past and picked up the signal as it transversed the 870 mile transit route.<snipped useful but irrelevant facts>