Technically, all of the teams can because they own the rights to those cars. However, if any other Formula 1 car were to be included and it raced against the Ferrari F10 - and especially if they raced somewhere like the Nurburgring GP circuit or Monza - then it would be in violation of the licence issued by FOM because it could be argued that such a race would constitute a Grand Prix, which Polyphony does not have the rights to. As there is no real purpose to the Formula 1 cars other than to race them against each other, there is no case for including multiple cars.