Considering how its a completely different console generation, I find that hard to believe. Still, any source I can read on that?
You can try Googling if you like, but there is a lot of misinformation out there.
For example, some people claim that it requires "system link", which is rubbish. FM2 supports system link, but it was dropped from FM3 and FM4 yet they both support multiple screens. Some people claim that you can connect multiple monitors to a single console via hdmi. That's rubbish too.
Here is how it actually works.
All that is required of the console is to have a network connection. Each console is connected to an Ethernet switch or hub. Each console gets to have a unique IP address on that LAN. Nothing else is required of the console itself. Each console has its own TV or monitor.
The game software provides the rest. It works in these configurations:-
Multiple (original) Xboxes running Forza Motorsport (original)
Multiple Xbox 360s running Forza Motorsport (original) in compatibility mode
Multiple Xbox 360s running Forza Motorsport 2
Multiple Xbox 360s running Forza Motorsport 3
Multiple Xbox 360s running Forza Motorsport 4
Multiple PS3s running Gran Turismo 5
Multiple PS3s running Gran Turismo 6
In each case, one of the consoles is defined as the "master", and the others (called "clients") are told what to do by this master. The master, for example, tells the clients what track to load, which cars to load, what livery the cars are wearing. When the race gets going, the master tells the others which camera to use (bumper, hood, cockpit etc). It tells the clients where all the cars are so all the clients have to do is render their angle of the track and the cars.
In the setup phase, the "options" part of the game is used to define the angle of view, the angle lost due to bezel width, and which role the console has, for example master, inner right client, outer right client etc.
The implementation is different in Forza and Gran Turismo in the details. In Forza, you define a starting angle for each console, and iirc, you can have up to eight consoles (views), including an optional rear vision mirror view. GT asks you to choose between 3 or 5 monitors and then each is assigned either a number from one to three or from one to five, counting from the left.
It is possible to define multiple driver stations each with multiple consoles. GT handles this by assigning IP addresses to the master consoles and telling the clients which IP is used by their master. Forza does it differently by assigning a unique token for each "system" or station.
Forza requires that you do not enter the game proper until all consoles in a "system" have Forza active on them. GT is more flexible in that having defined the roles, the consoles can be started in any sequence and will dynamically connect clients even part way through a race. If a Forza client locks up and has to be restarted, the master has to be restarted in order to reconnect. If a GT client locks up and has to be rebooted, you don't have to reboot the master. This might be an advantage of doing things by static IP address.
None of the above multi-screen functionality is inherent in the console or its operating system with the one exception that it's possible to use the PS3's OS to define a static IP address. In all cases, it's Forza or GT which is responsible for synchronization of the screens by communication of location data over the LAN from the master to the clients. The master handles collision detection, car movement etc. The clients merely render what the master tells them should be rendered.
Of course, the source data for rendering is provided by a copy of the game in each console.
So unlike the way PCs or Macs support multiple monitors using an expensive video card connected to one computer, this is done by connecting multiple computers (consoles) over a LAN and having the game keep the consoles in sync.
Hope this helps.