There is no single SymbianOS, rather there are various platforms of SymbianOS which have different APIs and different build environments and also they change radically between versions.
I worked on adding support for SymbianOS UIQ 2 and 3, but that UIQ platform was horrible, with the worse build system that I have ever seen. Now UIQ is dead. The only surviving SymbianOS platform is S60, and even this one is destined to die out in aprox. 3 years. Nokia is the last manufacturer still launching Symbian phones, and it is commited to drop the platform.
I have no idea about how S60 works. In short I'd say that nearly nothing is ready in the Symbian port for S60. I most worked on trying to hack around that horrible Symbian build mess, but I doubt that any of that work applies to the latest S60 because they change a lot between versions.
Felipe Monteiro de Carvalho