Microsoft actually has started a garage concept with a real garage inside one of the MS buildings... Some of the things that have come out of there: http://www.officelabs.com/Pages/ConceptTests.aspx
Microsoft's real problem is its top-down hierarchy and performance-ranking driven DNA, which fouls up whatever they step into. Superficial solutions like a garage or an officelabs are irrelevant to their bottom line. These are mostly costmetic and PR efforts.