From today, IT Administrators can bunch install Silverlight plug-in (1.0 of course), on all Windows machines on the network using Windows Server Update Services (WSUS). The plug-in is available from Microsoft Update, for more info check the Microsoft Update Team Blog.
The plug-in however is Optional (perhaps for the legal battles with other browsers) and is available as "feature pack", and will require accepting EULA.
But within two weeks, February 12 to be precise, Microsoft will push the plug-in with automatic updates program, from the Microsoft Download Centre, and the install will be again Optional but Windows Genuine Advantage (WGA) free. This is made available with the Internet Explorer 7.0 update as WGA free, for more information check knowledge base