Speaking as a Yahoo employee...
Firstly, Yahoo moving it's HQ to Dublin is nothing to do with operations per se. The former HQ was Switzerland, we left that because the tax advantages weren't good enough and came with too many caveats. Not a surprise to anyone with a brain, but the company was mainly run by the CFO at the time, so...
Secondly, I suspect the usual deal has been done with the Irish government to move some operations to Dublin. However, just like the other companies that move there, Y! has realized already that the "pool of English speaking experts" is a tad smaller than advertised. I interviewed in Google IR for a job in Australia, and I met engineers from many countries...excluding Ireland. Importing talent is expensive!
Thirdly, Y! UK will continue to comply with UK government court orders, just as it complies with Irish, German etc, just like any other company. Legally, Swiss government court orders have a bigger impact on privacy...