Read my post #250 in this thread. It looks like CBG customers who provided an ABN will be shunted off to Diners Club Land...
When I called Citi in early July regarding the CBG (after I received my letter saying that I would receive a Platinum card), I discussed several options with them for business use. During the call, they suggested the Diners card, and offered to waive a fee (can't remember if it was the first year off or free supplementary card). However, after that discussion, they did allow me to give them an ABN and retain the CBG.