I have a CB plugin that will allow an administrator to customize the userlist query and join it to other tables, etc. It gets called by...

$_PLUGINS->trigger( 'onBeforeUsersListQuery', array( &$queryFrom, 1 ) );

I would like to propose that the 3rd parameter be changed to the $listid, rather than hard coded 1.

$_PLUGINS->trigger( 'onBeforeUsersListQuery', array( &$queryFrom, $listid ) );

You can take a look at my plugin here.
www.pdxcode.com/downloads/joomla

Thanks,
-Rob Anderson