My further testing has verified that this is a limitation of EPDM. I've managed to work around it, but I think I'll submit an ER for possible future inclusion.
I have been trying to do the same thing without success. I found SPR#429437 in the SW knowledge base which describes exactly this problem, but says that it was fixed in 2008 SP5. Maybe it broke again in 2011....
I'm going to contact my VAR and see if they can find out more.
You say that you have "managed to work around it". Did you do this by switching to using a manual transition, or do you have a more sophisticated solution?