The RadTabControl is a custom control
not a user control and to use it with MVVM you'll just need to bind its ItemsSource property to some viewModel collection. You can read a help article on the subject here
I've attached a sample project demonstrating this so could you please examine it and if you have more questions feel free to ask.
Check out the new Telerik Platform - the only modular platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native apps. Register for the free online keynote and webinar to learn more about the Platform on Wednesday, February 12, 2014 at 11:00 a.m. ET (8:00 a.m. PT).