I have been to the factories of Lamborghini and De Tomaso back in 1997 but it was a trip organized by the Ferrari Club. We were allowed to take pictures everywhere we wanted. Great trip! I do not know if it is hard to get access when you show up. I suggest you contact them and ask.
Dirk, the picture of my car was taken yesterday where the Ferrari Club Nederland held their anual 'driving ability course'. Some 40 Ferraris turned up including a F40, a 575M, a 456M, a US spec 348 TS and a 348 Spider. A brand new Modena got unlucky and ended up with a front bumper damage.
Niels