While working at General Dynamics Electric Boat, I worked on several projects that had different project managers for different portions of the job. There are pros and cons to this approach. The good thing is that people are experts on their portion and have more experience and insight. This helps to foresee problems and mitigate them. The bad thing is that there is no real ownership. Yes, people are assigned this or that but they are working on lots of different projects and at the end of the day, only one manager is really responsible for it. Due to there being no real ownership, some managers might not take deadlines as seriously and there is conflict.