Epic's Lead Producer Jeff Morris told Kotaku that the mods will be created on a PC and then "cooked" to work better on a PS3 using a built-in option. That file can than be slapped onto a Memory Stick and imported into the PS3 version of the game with the console's built-in MS reader.
He said the company is also looking at ways of making the mods downloadable through an in-game browser on the PS3 and perhaps even Home.