Automated on-demand shuttles operating at SAE Level 4 are a promising means of improving public transport in suburban and rural areas, but their deployment depends on a remote operator who can resolve situations exceeding the vehicle's operational design domain. This paper addresses how to specify and implement a communication interface between an automated public transport shuttle and a technical supervisor in compliance with the remote assistance requirements of the German Road Traffic Act. Although standardization bodies such as SAE International, ISO, and ETSI have substantially advanced connected, cooperative and automated mobility, no technical specification of a communication interface for remote assistance of automated vehicles currently exists. To fill this gap, we adapted VDA 5050 – an established industry recommendation for intralogistics communication between mobile robots and a fleet management system – to automated public transport. We realized the interface by modifying an open-source ROS 2 implementation of VDA 5050, integrating it into the Autoware-based driving stack of a VW e-Crafter shuttle bus, and demonstrating its applicability through an interactively planned maneuver around a disabled vehicle during an end-to-end passenger journey. Supporting remote monitoring and several remote assistance concepts, and potentially extensible toward remote driving, the interface provides a practical, standards-based foundation for initiatives such as the forthcoming extension of the VDV recommendation series No. 435 and for the wider deployment of supervised SAE Level 4 shuttles.