No, they ask their IT department.
The difference being, they can fix issues with the OS themselves (or hire someone to). With something closed like Windows, there's only one place to go for support.
Access to the source code is one thing, but you'd need also developers who are familiar enough with the source to be able to actually make changes. With OSS, there is a large community from which you recruit these folks, with Windows, not so much (outside of MS).