"To be mapped against" can be used literally or metamorphically, as you said. If you want to map a literal journey (such as a road trip across the United States) against literal landmarks (like New York City, Chicago, and Los Angeles), this means to make a diagram of the journey while relying on those landmarks as the major points along the journey. The diagram is called a map because it represents geography. Your example is a more metaphorical journey (the team progress, as you pointed out) so the "map" and it's "geography" are also metaphorical: the landmarks are the four stages of progress. If you map the progress of several different teams, perhaps they would be slightly different from one another, but they should all appear generally similar in that they pass through those same four landmarks: forming, storming, norming, and performing. I confess, it's not easy to explain, but I hope this helps!