While many numbers stations of the past used state run shortwave broadcast transmitter facilities, typically they did so with separate programming from the normal shortwave broadcast transmissions. For example the Cubans, and V02/M08/SK01/HM01, they are known to use Radio Habana resources, probably both the transmitter facilities and the audio facilities. Radio Habana uses them for their broadcast programming, and the Intel users use them at different times, and different frequencies, for their numbers operations. But North Korea did not bother to separate them. They simply sent the the messages in the middle of scheduled PBS programming. However they stopped doing this in 2000. ENIGMA assigned it the designation V15, but as ENIGMA was mostly European based they never monitored the NK transmissions with regularity, and there may have been more than one format used. Japanese listeners probably had a better understanding of the NK transmissions, but there was not as much interaction between most of the European / American based listeners and the Japanese as there could have been, I think the language barrier was a big part of it.
It appears they may have restarted this practice. So far only one transmission has been noted, or at least generally reported, however that does not mean there have not been more that went unnoticed. If this is actually a process they are reinitiating time will tell, and we can probably work out some kind of schedule.
T!