Next generation mobile networks are envisioned to provide support for real-time control applications. One of the main aspects of these systems is that the location of the controller may be separated from the location of sensing and actuation. This promises benefits in terms of an increased flexibility, lower costs due to resource sharing, and higher computational capabilities. This paper focuses on one aspect of such systems, specifically, the controller handover. During a controller handover, a control process is moved from one point of computation to another at runtime. A possible reason for performing such a handover is to move the control process to a controller with better channel conditions. The safety of the handover is analyzed using a probabilistic reachability analysis by modeling the handover procedure as a stochastic hybrid system. Based on this safety analysis, a safety-oriented handover triggering rule is proposed. This triggering rule is shown to be dependent on the instantaneous state of the plant, in contrast to handover in mobile networks where it is only dependent on the state of the communication links. A vehicle platoon is considered as an example scenario, which is controlled by a base station of a mobile network. While driving, the platoon will move out of the communication range of the base station, so the control process needs to be moved to the next base station. Simulations illustrate the conditions for a safe execution of so called hard and soft handover protocols.