Having worked in a Telco environment, Manufacturing MNC, Government agency, Healthcare organization, aviation industry and my own startup company, I had the opportunity of working with different stakeholders, including those who have been in the organization for many years. I benefitted a lot by learning from resources who hold the domain expertise and in-depth organization climate knowledge.
From my end, having worked in different industry domains, I could contribute by bringing along a broader set of experience and knowledge on the use of technology as well as a strong management skill set of diversified user groups, domain experts and stakeholders.
One is not above the other. An experienced Project Manager would need these resources' in-depth knowledge of the industry domain as well as the organization culture and processes to manage the project effectively. Vice versa, these resources may not be able to function effectively as a Project Manager without any project management training.
What happened when a Project Manager possesses the experience and training in project management as well as the domain expertise? Well, he/she would be a well sought after Project Manager within the industry domain.