> As in, I go to a tfl ticket machine, touch, put money on, touch again and then I can use the card on the underground. Then I go to Southampton, go to a ticket machine, touch, put money on, touch again, then I can use the card on the Southampton's transit system.

Literally just tried this with the Southampton card in London against a tfl machine. No Dice.

Shame, but yeah, not really surprising.