Comment # 5 on bug 1204956 from Andreas Stieger

What the user wants is a zero-setup, distributed cache on a shared writable
path, invalidation without central instance or consensus, but with resilience
against hosts that are configured what he calls "anti-social" - DWIM.

Reporter, the reported behavior is expected. The local cache is treated as
such. The functionality is covered by RMT and another caching proxies at the
network side. For maintenance updates the bandwidth is greatly reduced by delta
rpms. You could build something opportunistic with rsync.