We'll check RFT in the next couple of weeks, but in any case that's something their support team should be better able to help you with. It depends on what general capabilities does RFT provide about calling cross-process .NET code, if any.

Do you mean [url=http://msdn.microsoft.com/en-us/library/dd320505(VS.85).aspx]this technology[/url]

It seems we would have to implement one of the provider interfaces for the control patterns listed below to let you access the diagram through UI automation:
[url=http://msdn.microsoft.com/en-us/library/ee671201(VS.85).aspx]http://msdn.microsoft.com/en-us/library/ee671201(VS.85).aspx[/url]

Which of these provider interfaces do you think would help you for testing the diagram? We can see nothing that matches the diagram object model.

Stoyan