The thing with Raynet, and often forgotten is that they are not only suppliers of the comms links, but free operators too.
If you have a large event, or real incident that is going to be at least a few days long, Raynet is an ideal solution, hence their continued involvement with the user services, same as the WRVS, Red Cross and St John etc. The comms traffic is Tier 1 - emergency and time sensitive, Tier 2, support and essential services, and then Tier 3 - the lowest level, but essntial services that have to take place, but would clog up the system used for 1 and 2. So it's the food, clothing, changes of shift data, names, lists, supplies and stuff like that. During a major incident, the people likely to be doing this are better used doing the important stuff, so the amateur agencies are excellent at this essential, but mundane stuff. Sticking somebody in the HQ who can produce the lists of stuff that are needed without clogging up Airwave or it's successor makes great sense, logistically. Doing the non-blue light stuff has to be done, and if staff are short - using volunteers works brilliantly, because they organise themselves and the real user services just use what they produce with no staf implications.