Given people's limited time, NDAs, etc, I'm not expecting all my questions to be answered here, but if nothing else this is a handy place to park them.
OK. In addition to its Lua scripting support, CryENGINE2 also supports compiled C++ extensions - see
Programming Manual
Since the C++ dlls are generally used to make fundamental changes to the world, I would not be surprised to see them only available to City Developers. It might be a tad confusing if gravity was reversed in your neighbour's store for example.
If that unsubstantiated speculation is correct, it will be interesting to see where the functionality-line is drawn between what the Lua scripts have access to, and the C++ dlls.