I have only found this out today (15th June)....not sure how long its been valid or how long for, but if you insert the following product code into Origin, you get the 'Close Quarters' DLC free of charge.
BF3E3
Just open Origin, click on the 'Origin' menu at the top left of the screen and select 'Redeem Product Code' Enter 'BF3E3' and you should be able to download it straight away.