William Tay (Aka Softwaremaker) one of the most knowledgeable WSE guys around has published an excellent article about interoperability between WSE 2.0 and WCF.
I usually find people concerned about topics like this, the different interop issues between WSE 2.0, WSE 3.0 and WCF.
Well, this article really helps clarify the required points to make both products work together. In addition, it includes some code samples.
You can find the article here