New blogs are available now detailing steps for extending Coded UI Test to work on 3rd party controls or custom controls. Users who have been facing issues with adding test support to custom controls can refer to the guidelines listed on the blogs.
http://blogs.msdn.com/b/visualstudioalm/archive/2011/10/28/coded-ui-test-extension-for-3rd-party-controls-the-basics-explained.aspx
This blog explains step-by-step implementation of extension with each step allowing access to rich features of Coded UI Test on custom controls. You can find clearly laid out usage scenarios with- or without- step implementation.
http://blogs.msdn.com/b/visualstudioalm/archive/2011/10/28/coded-ui-test-extension-for-3rd-party-windows-forms-controls-how-to.aspx
This blog takes a deep dive into real implementation of each step on a 3rd party control and shows code required to achieve all desired functionalities