I work in a similar environment. I certainly agree that the convenience of have an entire, or a majority, of the department be familiar with the ongoing projects means that if an individual is unavailable you can seek help from another in the department. I found this especially helpful in the case of documentation control department. Many of the projects I am involved in require new documentation release or procedure updates that have to be approved by doc control. This is often a bottle neck as there is a great deal of projects that require similar review. Having a matrix organization allows for priority projects to be given to any of the personnel in order to speed along its review process.