Most likely a targeted offer and AMEX issued cards only.
I noticed it as on offer on the new amex online banking. Log into AMEX online and go to your account summary (MY ACCOUNT then Your Account option). There is now a few tabs:
Available directly on Amex Rewards site.
Amex and bank issued cards.
Spend $90 or more at Country Road branded stores or online before 12/1/14 to receive one $30 statement credit. Limited to first 10,000 Cards to register. Other exclusions apply.
Please read the Offer Terms
OFFER TERMS
Offer only applies to spend on this Card. It does not apply to spend on any supplementary Cards on this account or any other American Express Cards you might hold. Supplementary Cards and Bank Issued Cards qualify as an Eligible Card only if they register for the offer separately at amexconnect.com.au
Cardmembers must register by saving this offer and spend $90 or more on their registered Card at Country Road instore or online at countryroad.com.au, in one or more transactions, between 9/12/13 and 12/1/14 to receive one $30 statement credit.
Participation is limited to the first 10,000 cards to register.
Gift Card purchases or purchases made through concession stores in department stores; online aggregators such as Paypal or other retailers are excluded.
Statement credit is normally issued within 3-5 days of the eligible spend, but may take up to 8 weeks to appear in your account.
Statement credit may not be applied to your Card Account if it has been suspended or cancelled and may be reversed if qualifying purchase is returned or cancelled.
General terms and conditions available here
Included Bank issue AMEX ?