This Forum thread relates to RadControls for WinForms, but I will address your question any way. It will be best to check the Telerik Silverlight Forums for more in-depth answer to your question.
Indeed, currently only very few of RadControls for Silverlight have UI Automation functionality. We are aware of that and we are planning to provide extended support for UI Automation in 2011. Here is the list of what is supported currently: Silverlight UI Automation
the Telerik team
Q3’10 SP1 of RadControls for WinForms is available for download
; also available is the Q1'11 Roadmap
for Telerik Windows Forms controls.