I think I will need to ask Lindsay what all the RRDB stores and what all the RR SOAP Web Service provides, to understand how they correlate in order to help people make more sense of this. Right now its still as clear a mud.
One means that might get you to the end you want (which entities need to have native tags) would be to look at the location reports that you can get for any trunked system or county page on RRDB. Click on the "Download and Reports" tab an view the location reports. This shows only "native" (not inherited) information, so if a tag isn't set, the line is blank.