Google’s Icon Repository→
At large companies such as Google and Microsoft, where software is deployed across hundreds of products and services, icon design is done by in-house teams. Google’s approach is a blend of design and engineering: Icons are treated like code and housed in an open source repository. “There’s one ‘pause’ icon for the whole company, and if we tweak it, the changes propagate out to everybody automatically,” says Josh Estelle, who leads the material design engineering group.
That’s actually a really great way of doing it – it keeps the design language consistent across their (admittedly rather sprawling) set of services and apps.