An aquaintance who is already a jobbing ATCO for the IAA seems think that they'd only discuss salaries if they were going to make a job offer, i.e. you'd have to go through the interview process.
He also said that if they were three year contracts, it's highly likely that it's because they haven't recruited/trained enough of their own recently and it's to cover that shortfall, although there doesn't appear anything to be on the IAA site at the moment.
Word is that although they may have to pay a decent salary to get the experienced atcos they temporarily need, they wouldn't pay relocation costs and you wouldn't be allowed to join the pension scheme.
Would it be worth anyone relocating half way around the world to go there for such a relatively short time? given that the cost of living in Ireland is at least on a par with most of the UK (i.e high), it seems not.
But with plenty of cheap flights to and from the UK, anyone from NATS could commute if they could bear it, thereby taking a very pleasant sabbatical I would have thought.