Catena-X assigns unique identifiers to legal entities, sites and adresses https://meta.cdq.com/BPN_(World).
A linkage based on this identifier should be possible between the CX Pool and any CX Mirror. Criteria for the linkage quality should be city and postal code with a relatively low threshold (only if the adress is very different a review should be triggered since the BPN is a very distinctive criteria.)
Actually, a technical differentiation between CX context and regualar sharing context might not be required since only CX members will be using the CX BPN.