I'm glad I came across this thread as I had the same question and thanks for the tip that Cardzone are the people that now fulfil the redemptions.
I got in touch with Cardzone today and their response was to mail the redemption cards via registered mail to:
Card Zone
169 Peel Street,
NORTH MELBOURNE, VIC, 3051
and include a "self addressed prepaid REGISTERED ENVELOPE" along with the cards. I got three redemption cards in my box (two sigs and the Watson shirt card!) so I'm glad I can redeem them!