Originally Posted by
AutoSlash
Book with the IBM code and ask them to switch it at the counter to the Amex Platinum CDP.
As you probably surmised, one benefits of the IBM CDP is guaranteed availability even when they are sold out. Also, keep in mind that the IBM contract has very reasonable fixed rates, so it's hard to predict what the Amex Platinum CDP will yield, but you can always ask before they switch it.
Thanks for the reply! Is it clear that they won't say at the counter "No, sorry, that car is reserved for IBM so we can't switch the CDP ... oh and while you're here, show us your IBM credentials or we won't rent you a car at all"?
I'm guessing I'm being paranoid, but...