I would say that a company should have a communication management plan and document it as an SOP. It should be a broad plan though and include what every communication plan would have. So with different projects, the team should make sure they follow this SOP and add on anything specific to their project. I think a controlled document like an SOP is necessary because sometimes someone on the team may not have experience with communication management plan and it makes it much easier for everyone (the whole company) to be on the same page.