The source of uncertainty is usually customer demand, travel time, service time at the location (during pick up or serving the customer), or presence of the customer (customers may not be available to receive their orders). As mentioned in the paper:
Capacitated vehicle routing problem with stochastic demand has been by far the most studied version of the problem.
This paper "The stochastic vehicle routing problem, a literature review, part I: models" reviews these different cases. In another review, the same authors discuss different solution methods.
About queueing theory idea for solving SVRP, you can take a look at this paper: "Vehicle routing with dynamic travel times: a queueing approach" where:
a vehicle routing problem with dynamic travel times due to potential traffic congestion is considered. The approach developed introduces mainly the traffic congestion component based on queueing theory.