SAGA is a high-level programming interface which provides the ability to develop distributed applications in an infrastructure independent way. In an earlier paper, we discussed how SAGA was used to develop a version of MapReduce which provided the user with the ability to control the relative placement of compute and data, whilst utilizing different distributed infrastructure. In this paper, we use the SAGA-based implementation of MapReduce, and demonstrate its interoperability across Clouds and Grids. We discuss how a range of cloud adaptors have been developed for SAGA. The major contribution of this paper is the demonstration - possibly the first ever, of interoperability between different Clouds and Grids, without any changes to the application. We analyse the performance of SAGA-MapReduce when using multiple, different, heterogeneous infrastructure concurrently for the same problem instance; However, we do not strive to provide a rigorous performance model, but to provide a proof-of-concept of application-level interoperability and illustrate its importance.