Reorganization activities in the enterprise require a systematic approach to evaluating the results of individual projects. Currently, in order to improve competitiveness and the need to meet new business challenges, many companies implement business processes reengineering projects. Even the most well-judged processes reengineering decisions in practice demonstrate lower effectiveness than expected, because during the implementation uncontrolled factors are revealed. A systematic approach to the implementation of such projects involves consideration of any organizational change in the context of enterprise architecture: it is necessary to take into account the interconnection and interdependence of business processes, organizational structure, information systems, IT infrastructure and other components of the enterprise architecture. In practice, the reorganization projects are often implemented in isolation without taking into account the existing relationship of a particular component of the enterprise architecture with other ones, which leads to unsatisfactory results of projects. In this paper the approach of the service-oriented analysis of organizational changes for business process reengineering was described, and the application of this approach was demonstrated in the project of business processes reengineering in the Saint Petersburg underground railway.