The all cars code does not unlock the cars in the arcade. I have one PAL save I set up with the Xploder to get all the cars and there were still only 250 cars open in the arcade. I presumed this would be the case as I already checked out a similar American save.
I am using the save for trades though even that does not get them into the arcade. I prefer low mileage examples in my garage (for the extra HP) and buy a cheap used version first and then use a memory card trade to buy the low mileage car and then sell the high mileage one.
