Its 12 cars for the Deluxe Digital Edition, they may well be included in other editions.
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However I do find it interesting that some within the community seem to have ignored this, given that every time its happened with other franchises its been akin to the devil's work. However I'm sure they will be made available as a standalone DLC down the line, but given that you pay an extra £10 for the deluxe version in the UK I don't see it being free DLC.
Whatever your view on the morals behind this kind of practice, given the size of the car list, this just makes matters even worse for the base editions.