Bosnich is preparing for next month's glamour friendly against LA Galaxy after being selected to be part of the Oceania Allstars.
Sydney keeper Ivan Necevski told the Sydney Morning Herald: "He started training with us on Monday and he's just great value … although it's a bit hard to concentrate with him yelling all the time," Necevski joked. "It's good to have him there and it's good for us up-and-coming guys to have someone of his calibre around. I wouldn't mind if we signed him."
Former Wigan No1 John Filan is also on Sydney's books.