At Semantic Machines [0] we rely heavily on probabilistic programming to build state-of-the-art dialogue systems. In particular, we use a library called PNP (probabilistic neural programming) on top of Dynet to allow us to express structured prediction problems in a simple and elegant form. If there are questions I am happy to elaborate to the extent I can. (Also, we are hiring! My email is jwolfe@.)
[0] http://www.semanticmachines.com/