Thank you for your comment and question. In our third post, we try to bring in political aspects of evidence-informed decision-making by considering the reasons deemed relevant by a wide variety of stakeholders to decision-making. This process, in turn, brings these contested views of what types of evidence and other considerations matter into the the design of the evaluation itself. We welcome your views on that post once it is up and you can let us know if it at least hints at the political question you are asking.
At present, we feel the 'big data' argument is slightly beyond our scope, which is an investigation of a test case of 'small data' being commissioned explicitly for decision-making. However, we agree that it is a point that should be explored.