They have. Your corporate contact will have access to it to upgrade your PC. It's also in MSDN for developers if you are using it on a small scale. Don't expect an upgrade prompt like Home versions.
I had a TechNet subscription and one of my PCs in my den I was playing around with Windows Server and the enterprise version. Is there anyway to get the windows 10 upgrade on this machine when you don't have a corporate admin? The Volume License site really would work in this situation.