This paper proposes an analytical model for characterizing the impact of the users' mobility in the multicast subgroup formation problem when the aggregate data rate is maximized in Long Term Evolution (LTE) and beyond systems. We demonstrate that, under the condition of constant number of multicast users within the service area, their mobility can be modelled as a queuing network. The proposed model has been validated with the most relevant multicast mobility simulative approaches proposed in literature. The high relevance of this result is that the proposed model can be easily exploited to characterize the user mobility in practical LTE systems to avoid the heavy-processing burden of solutions based on simulative approaches. © 2017 IEEE.