From a SW point of view, the 'arrangement' is as bizarre as you put it. To get JB/JA, one must be available for and genuinely seeking work. every school holiday, thousands of terachers, school cleaners, bus drivers, lollipop people trapse into Sw to claim dole until they go back to the same employer when school opens again. They go through the same hoopsthat all unemployed people go through, but a blind eye is given to the fact that they really have no intention of working for the period they are out (what person would take a job for two weeks at Christmas time when they know that they will be going back to one in early January and, for that matter, what employer wouldm take on somebody like that?).
What happens is that the 'Live Register' is bumped up at these periods and the claims clog up the system, especially in the current pressurised climate within SW.
But regarding the p45, these are not given in general, or looked for. A letter from the school outlining what holiday pay has been given suffices. I might add that the HSE are alos manipulating the SW system in this way by employing 'temporary' staff, some of whom have been in HSE on and off for ten years or so! There is aslo the issue that these people will never qualify for redundancy.