Actually, it is possible to cheat in Tron Evolution on the PC.
However, revealing how it's done would also allow people to cheat in Multiplayer. So, I'm afraid I'm not going to explain how. It's also possible to use these cheats in the console versions. Which is why you're seeing people cheating in the 360 and PS3 versions as well, in Multiplayer.
What I will say is that, for example: it's possible to put yourself in God mode, fly around the map, and put everything into slow motion.