the short answer is that it will be one class at a time.
there was a rumour that it would be 12 iaa cadets, and 12 icelandic cadets on the same course - this was done sucessfully before in 2000, but i dont believe that this will be the case
25 on a course seems a little high. given that on the job training would have to be staggered. all iaa training as a cadet will be in shannon. they may require some people to work in dublin - they train in shannon too!, but i doubt if the iaa know the exact breakdown of where they want the staff to go at this time.
most trainees end up as shannon controllers, and we have 8 different watches. normally it would be 1 trainee on ojt per watch, 2 max. recently it has been broken into groups of 6 trainees per rating course.
the iaa like to make up a panel, so e.g if they need 12 on a course, they will also bring on 12 more to final interview with a view to starting them about 6 months later on. this is what i meant by 1 class at a time. going back to 98/99 they made 3 courses from the same recruitment, but those on the 3rd course did not begin for at least 12 months after the first course had started.
the 2 main constraints on class numbers are (1) simulator capacity: currently there are only enough sims to have 6 in the sims at a time.
they have run courses on a pseudo shift pattern to facilitate 12 people, but instructors come from the operational area, so constraint (2) is we're short enough on staff as it stands without releasing double the amount of instructors
if i get any further info, i'll post it here.
its possible others with more/better info, will also chip in