I have no personal experience with those 2 particular breeds but I do have a theory. Depending on the age of the new dog I believe that it could work with the proper meet and greet and socialization. I would definitely recommend crates for the two dogs where they each have a "safe zone" to retreat to. My two dogs are not the same breeds but they are both extremely bull headed. I'm blessed that they got to know each other in a good environment. Apparently the other day (I didn't see it but hubby told me) the rat terrier grabbed hold of Gunther's side and held on as he ran through the yard. If things hadn't been done to socialize correctly this could have ended in horrible things I don't want to imagine for both dogs. The terrier is 6 years old, shows no signs of submission and yet no signs of dominance. Again I know this is no comparison in breeds but the same personalities apply. It comes down to proper socialization. Hope this rambling helps a little.
Hail Gunther 7-2-2013
If at first you don't succeed, destroy all evidence that you ever tried.
"Some people never end up going crazy...what a truly terrible life they must lead." - Unknown