I have experienced this quiet a few times as I work closely with PM’s. So anytime there is a change in a PM, due to any reason either the PM leaving or a senior PM taking over the project, there is always a kick off meeting to go over the project scope and the completed tasks as well as the uncompleted tasks. Anyone who plays a role in the project is part of this kick of meeting so all aspects and tasks of the project can be addressed. A new game plan (project scope) is created in this kick off meeting. From this kick off meeting the new PM learns if new resources are needed for any tasks that were newly discovered or if they can delegate people to specific tasks.