<span lang="en">This paper deals with the performance evaluation of deploying an IMS-based media plane interoperability framework. The 3GPP standards describe two possible operating modes based on either a reactive or a proactive approach. We show that both approaches entail some advantages and drawbacks in terms of signaling overhead and call setup times. In order to use experimental individual delay contributions, a prototype implementation of the required elements was carried out for which transmission and processing times and the average ratio of incompatible calls where evaluated. Additionally, the evaluation focuses on the impact of deploying the interoperability solutions over current UMTS and LTE radio access networks.</span>