This paper presents a queuing model to evaluate the performances of cooperation mechanisms in 4G/5G cellular networks. The main contribution is the proposal of an approximation model with a closed form formula allowing fast numerical evaluation of throughput and loss probabilities per service class, while considering traffic load, radio conditions and the available resources in each collaborating cell. The proposed queuing model is successfully applied to the enhanced Inter-Cell Interference Coordination mechanism with service differentiation in the context of Heterogeneous Cloud based Radio Access Networks. Numerical results are compared to Matlab simulations with realistic radio conditions and user distributions. Through it, decisions on resource allocation among the cooperating cells to achieve the optimal capacity of the system become faster and adaptive. In conclusion, the proposed queue-based model can be used in order to tune the front-haul links and the core network resources.