Ticketing arrangements have been made so that at most, the extra passengers will be between London Bridge and Waterloo on the Jubilee, or Cannon Street to Embankment. They can also use buses between London Bridge and Waterloo (tickets will also be valid on the Bakerloo and Northern from Waterloo to Charing Cross) and Cannon St to Charing Cross.
Southern tickets will NOT be valid between NXG and Canada Water on the Overground, which I suspect is to discourage overcrowding on the already busy services which will keep them on the normal trains into LB.