It is for Silverlight and explains how to use ContainerBindings, which is almost the same as using Style bindings in WPF.
The article explains how to bind the IsSelected and IsExpanded properties of RadTreeViewItem, but does not explain how to bind the CheckState. That is why, after going through the article, you can take a look at the attached sample projects.
The ContainerBindings.zip contains a Silverlight project demonstrating the functionality you are looking for, and StyleBindings.zip is its WPF equivalent.
Give it a try and let me know how it works for you.