Currently the documentation of Enterprise Architectures (EA) requires manual collection of data resulting in an error prone, expensive, and time consuming process. Recent approaches seek to automate and improve EA documentation by employing the productive system environment of organizations. In this paper, we investigate a specific Enterprise Service Bus (ESB) considered as the nervous system of an enterprise interconnecting business applications and processes as an information source. We evaluate the degree of coverage to which data of a productive system can be used for EA documentation. A vendor-specific ESB data model is reverse-engineered and transformation rules for three representative EA information models are derived. These transformation rules are employed to perform automated model transformations making the first step towards an automated EA documentation. We evaluate our approach using a productive ESB system from a leading enterprise of the fashion industry.