@Wire_Mark - agreed, but so far as I am aware, ERCs are to be found in sparsely populated interior regions, like Australia, Canada, Russia etc. I don't know if there any in the area under consideration.
On the 19 whose phones have "rung", thinking about it, I suppose the home network could be configured to provide ring tone to the calling party while the mobile is paged. This isn't done in European and N American networks, but I don't know about China. I do know that so called "Colour Ring Back Tones" are very popular in Asia, where the caller hears music while the called party is located. This may be behind this story. Either way, examination of the signaling records will reveal whether it is "synthetic" ring tone, or the mobile genuinely has responded to a page. I expect the Chinese have looked into this.