This document describes the work undertaken by Task 7.2 "Joint Access to Data, HTC and Cloud Computing Resources" within the EUDAT2020 project focusing on the interoperability between EUDAT and EGI. The main objective of the conducted work was to realize cross-infrastructure services that enable the desired perceived seamless access to a combined infrastructure offering by both EGI and EUDAT services in pairing their data and high-throughput computing resources together. This document concentrates on the phase after the definition of the generic use case and depicts in detail the challenges encountered by the early adopters, the resulting new requirements and the identified solutions.