Well, let's think about it a bit more
"...a quarter of UK staff being kicked off its final-salary pension scheme" [in 2009].
However, since about 1997, new hires have of course not joined the Defined Benefit scheme since it was closed by then. So we're talking about people who've now been with IBM for almost thirty years or more, and have not yet accepted a package. So whatever the legality or ethics of it, we aren't actually talking about a very large fraction of IBM UK staff. The majority of the staff, on a Defined Contribution pension scheme, might feel aggrieved at the impact of this decision on the pension fund as a whole.