The extraction of hard rock in quarries is based on drilling and blasting, loading, haulage and processing technology. A method for comparing the work of stationary and mobile processing plants has been presented. It has also been shown how to calculate the probability of the aggregate flow depending on the types of connection. Elements of the processing systems can be connected in series, in parallel or in combination, which fundamentally influences the system's operational stability and efficiency. Each element of the processing system has been calculated by the operational probability, which has made it possible to determine the operational probability of the whole system depending on the way of connection and partial probabilities of the elements of the processing system. This method enables forecasting the capacity of a processing system with regard to its potential capacity.