I don't have a way of testing this but maybe this unlock mod might allow you to access them. https://www.nfsplanet.com/download_sel.php?file=nfsshift2/files/shift2_unlock_cars.zip. Worth a try anyway. Remember to backup the file in case it breaks the game. If this doesn't work then you might have to do other methods I probably wouldn't be allowed to mention in this forum.
The nfsplanet zip file replaces one file in the game. This will unlock all Limited Edition content, and also the promotional stuff like the Dr Pepper Camaro. Although the cars are unlocked, the cars will not be free as they would be if EA hadn't broken the server that sends the unlock content messages to the game. If you restore the replaced file from the zip file back to the orginal file, the additional content cars in a save made available by the unlocked version will not show up. If you have an old save with the Limited Edition cars, it will still work with the replaced file.
