Sorry for the delay in replying.
The lockdown is being performed on the root account. As it is a local account and cannot see the domain, there are no items populated in the /User/Shared folder
As for editing the com.apple.sidebarlists.plist file, if we could find a way of opening it so that its contents appear in a descriptive manner so that we could edited it, then that could be a possibility. However even if we could do that, how could we use that file so that every users picks these settings up everytime they login?