I've seen several posts on various forums where folks are looking for samples showing how to build an MP containing linked reports.  The report authoring guide refers to some sample files but, those files don't exist anywhere.  I just finished up some linked report training and, as a part of the training, build out a custom linked report MP that is attached to this post.  You can also review how to build linked reports by simply exporting most any of our sealed MP's and searching for the linked report section.