It's not as strange as it sounds.
You have certain, demountable units is the official term, that carry general equipment that can be used by any crew at an incident, such as lighting, foam, salvage, breathing apparatus, command, haz subs etc.
You then have other pods, sorry demountable units, that carry major rescue equipment, environmental equipment etc. that have dedicated crews who are specifically trained in their use and turn out to any incident where the unit is required.
They have the advantage that the prime mover (the lorry that carries them) can turn out to the incident, drop them off then collect them when they are finished with, but in the meantime remain available to deliver other units should they be required.
It's not great being on a pod station as you are forever carrying out inventory checks and cleaning/maintaining the equipment carried on them, as not many people look after them at an incident as they are not usually from their home station.
I must admit I've been used to them for the last 21 years, and I think that they are a very good resource.