Tough call, it used to be in the registry, but as you indicated has been moved to the preferredservers.dat. The file changes often. The only way I can see to do it would be to script something to strip out the delimited server list from the file and dump it into the inventory. Would be cool to have it in the inventory. Also be nice to look at a package that has been deployed and see what server it was installed from without pecking through logs.
Installed By: Name
some crappy server\share.
I could add preferred server listing to ldms_client pretty easily, if there's interest. Parsing the logs for what got installed how sounds like a nastier job though.
It would be great to add that functionality to ldms_client. My intention for finding the PPS for each node is that we are moving towards using the newer PPS setup (adding servers in the console). With the query showing which PPS is for each node I can determine which nodes do not have a PPS and add the subnets to the correct PPS (think I can't use the acronym PPS one more time?...PPS! Ha! ).