I thought the benefit "harmonization" only started in US. GE pension plans also differ in different region, so most likely fellows in UK will get to keep their pension. For US, I don't think GE benefit was any where near BHI so I feel sorry for those legacy BHI employee that were harmonized to our crappy level. On the other hand, that's probably part of the strategy to achieve cost synergy through voluntary attrition.
As for why we legacy GE stay with such benefit, first it didn't started out like that, it's gradually reduced following our near bankruptcy in 2009. And secondly, at least for me, we can pretty much work on any industry, from aerospace to transportation to health care, just inside the company without losing the pension and can continue accrue year of service. If GE bugs out of BHGE and cut that link, Lorenzo better have some good compensations for it.