It is common for infrastructure builders to call upon consultancies to help them implement stakeholder and public dialogue approaches. It is however less common for them to work together within a dialogue framework over several years in order to make the infrastructure planner improve its participation and dialogue policy. This paper aims to explain the framework that has been progressively implemented by experts of public participation and stakeholder dialogue at Réseau ferré de France—the public company responsible for management and development of the French railway network in France—, and Arenes, a NGO that works as a consultancy. The specificity of this dialogue is due in particular to the hybridization between the research and practice of the two organizations, and ethical and strategic questionings or positionings. First, this paper explains the various frameworks of action and tools that this dialogue is based on: public debate and its preparatory dialogue, territorial diagnostics, the dialogue and public participation charter, and the reference documents of the company for developing its dialogue policy. This paper then analyzes the conditions and the main effects of this cooperation: whereas this experience shows a major interest in projects led in collaboration with methods and questionings of research, it also shows the difficulty of integrating outcomes into the strategic choices of a public company.