Is Git Scalable?

I'm thinking on use Git in my projects. But I have a doubt I couldn't resolve in the Git Docs or Wiki. My organization has really big projects that we split in sub-projects, like this:

Big Project
  \---> Project A
  \---> Project B
     \---> Project B1
     \---> Project B2
     \---> Project B3
  \---> Project C
     \---> Project C1

and so on...

Now it's possible to work in each "small" project independently (like "git clone ProjectB3") or you can work with a big project inheriting its sub-projects (like "git clone ProjectB" that automatically makes a "git clone ProjectB1", "git clone ProjectB2" and "git clone ProjectB3", putting each sub-project in the right place).

The question is: does Git support something like this?