Do these "internal" lists have "Confidential= Yes" or "Confidential= Service"?
I suspect however that what is getting sent is stats, not list information
per se.  What comes right before the list of servers in the log?  My guess
is that this is a SUPD job rather than a LUPD job.

Basically the only way you can stop the inter-server chatter altogether
is to run the server in STANDALONE mode.

Nathan