Imo, if you are managing a team of people, you're a manager whether or not you have total hiring / firing power.
is there something about their ability in this regard you don't trust? then, why are they a project manager? the success or failure of the project could impact the jobs of all of the members of the project, and potentially everyone in the company. why will you trust this responsibility to them, but not the ability to fire individual members of their team?
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Where I am right now, we report instead to technical managers, and are allotted to project managers' projects based on scheduling availability, project importance, and a number of other factors.
With due respect, I think your notion of how interpersonal relationships work in this sort of situation is rather flawed.