We show how transfer matrices of higher spin vertex models (generalizing the six-vertex model) can be conjugated into stochastic matrices describing interacting particle systems. Bethe ansatz produces eigenfunctions and we prove their completeness on the line. This, along with a self duality of the transfer matrices, provides a means to study the long time behavior of these stochastic systems. These considerations bring under one roof, all of the recently investigated integrable probabilistic systems in the Kardar-Parisi-Zhang universality class.