In this study, we investigate the use of intelligent reflecting surfaces (IRSs) in multi-operator communication systems for 6G networks, focusing on sustainable and efficient resource management. This research is motivated by two critical challenges: limited coverage provided by mmWave frequencies and high infrastructure costs associated with current technologies. IRSs can help eliminate these issues because they can reflect electromagnetic waves to enhance signal propagation, thereby reducing blockages and extending network coverage. However, deploying a separate IRS for each mobile network operator (MNO) can result in inefficiencies, redundant infrastructure, potential conflicts over placement, and interoperator interference. To address these challenges, in this study, an IRS sharing system is proposed in which multiple MNOs collaborate to use a common IRS infrastructure. This approach not only enhances network flexibility and reduces costs but also minimizes the effect of interoperator interference. Through numerical analysis, we demonstrate that IRS sharing effectively balances performance and fairness among MNOs, outperforming MNO-specific deployment methods in multi-MNO scenarios. This study provides insights into the potential of IRS sharing to support sustainable 6G networks, thereby contributing to the efficient deployment and operation of next-generation wireless communication systems.