How exactly does static batching work in Unity?

I know what static and dynamic batching are, from the perspective of implementing a rendering engine in, say, OpenGL. My question is towards how specifically it works in Unity Free.

For example, if I mark a bunch of scene elements (floors, walls, etc.) static, and they share materials, will they be collapsed into one draw call?

If I use empty game objects for organizing scene elements (say one to hold floors and one to hold walls), or to simply scale some elements (e.g. make a selection of bushes half size), will that introduce extra matrix multiplications at runtime, or will the static batching process effectively optimize it all away?

Are there any resources which explain the nitty gritty details of how Unity Free takes a hierarchy and renders a scene?