I have never heard of multiple project managers for the same project. There can only be one project manager per project. There are department managers involved in multiple projects or one project manager involved in multiple projects. The way a project is being led by the project manager depends on how the organization is structured.
There are 3 types of organizations: Functional, Matrix and Projectized. Functional organizations are where employee has one clear superior. In funcational organizations, Project manager has little to no authority. Projectized organizations is where the project manager has the project authority. He has jurisdiction over the project’s budget, schedule, and the project team. Matrix organization is a combination of functional and projectized organizations depending on what type of matrix structure is being run.