The sides in the BART labor dispute are set to return to the bargaining table this evening.  That's according to the state mediator who is overseeing the negotiations. The BART system has been shut down since early Monday morning after union workers walked out following the expiration of their contract. The main issues standing in the way of a new contract agreement include wages, benefits and worker safety. BART is the Bay Area's largest transit system carrying an average of 400-thousand passengers on weekdays.