Something that might be worth mentioning: a few years back, a group ran a project similar to this in which they were trying to see what the crypto hobbyist community would make of numbers stations run over the phone. They ended up presenting their findings at Defcon [link to www.defcon.org] , and their old website (which is currently inactive) has been archived [link to web.archive.org] . I'm not saying it's them doing the same thing again, necessarily, but it could easily be another person or group trying the same idea out.