it's not a problem at all. as far as CO is concerned, they have no way of knowing where the points came from, unless they go looking at your statements to see the AMEX transfer.
in some ways it is actually easier to book awards. if you don't have the miles in your account yet, tell the agent that you are transferring miles from AMEX. they will allow you to hold the space and note in the record to not cancel the space "pending AMEX points transfer".
------------------
Bad Gordon!
No Freddie for you!