Before that last post gets out of hand, there are a few things which should be pointed out. Yet another case of my mate told me, and he heard it from x etc.
Many of the people who are on the ground are seconded crew - it would be they who are called upon, and they have extensive experience as crew - a quick refreshers course, or recency exam and off they go. Many of them fly regularly anyway - CPM's, Training Instructors, Service Delivery etc.
Anybody else from another department would operate as non-required crew, therefore there is no legal reason for the CAA to become involved.
Remember the company are doing this to ensure minimum disruption for our passengers - a welcome move.