There’s an interesting four page PDF file that appeared recently on the Microsoft downloads site titled…

Open Source at Microsoft CodeBox: Bringing the Open Source Approach In-House

It answers the question: Could the community and collaborative concepts that
underlie open source projects be applied internally to Microsoft product engineering?

CodeBox is an software development environment that was developed as an internal tool to help Microsoft apply the Open Source software development model internally. It gives Microsoft’s programmers and internal tool to manage shared code.