Check this link:
Flight Operations Branch - Category II/III ILS information
You will find two Excel sheets that can be downloaded; one is a list of US CAT II/III runways, the other a list of foreign CAT II/III runways. These are the FAA AFS-400 master lists, and they are updated as necessary.
Jeppesen constructs the tailored charts first by reference to these documents, and then by reference to your company's Op Specs. They publish the most conservative minima between the two sources. Most US runways are still limited to RVR 600, so that is what will appear on your tailored chart even though you have Op Specs approval down to RVR 300. On the other hand, if your Op Specs approval is limited to RVR 600, then even those runways that are approved down to RVR 300 will be published, on your tailored charts, as RVR 600.
If you have a generic, non-tailored CAT III chart from Jeppesen, it will only reflect the AFS-400 minima, and not your company Op Specs.
At least that's the idea.