I think you misunderstood me. I'm talking about this note:
NOTE: as of August 2007, database dumps for Wikipedia and other Wikimedia projects as provided on http://download.wikimedia.org/ have incomplete data in this table: only redirect pages that have been created or edited recently are present. For older redirects, resort to using the pagelinks table.
My question was: what is the status of it currently - as of August 2015?
About wbc_entity_usage. OK, that seems normal, but where I could find, what DB tables are available for work at quarry?