I do know that the manifold (Y pipe) will fit. The 600 has a larger inside diameter than the 500, but it works great. I installed the XC 600 manifold on my XC 500 and it worked great...gave it better flow.
I also know that the B&B can that I installed on my 99' XC 500 fit the XC 600 as well.
I don't know if the pipe itself will interchange. I would assume that it would...but you know what they say about the word assume?
Call your local dealer and get the part numbers for the pipe and factory muffler for each model...that should give you the answer you are looking for.