I'm still trying to work out why they're paying GlobalFoundries to take the plants. The pension argument doesn't make sense - IBM switched from "defined benefit" to "defined contribution" about ten years ago, so they can walk away on a whim now. The only factors I can think of are:
1) IBM received a decent subsidy ($600M) from the feds to run a "trusted semiconductor foundry" line, on US soil (google it - not a secret). The government does this in several markets and industries just to make sure they prop up at least one US supplier - they used to pay Micron to make RAM in the US (and may still). Seemed at the time like they wanted to support "one architecture in addition to x86", which would of course be POWER. So, would a shutdown have triggered a repayment clause?
2) Or... semiconductor manufacturing is a nasty business - literally. Maybe it's cheaper to pay someone to take it than it is to clean up all the, say, arsenic that various processes use a lot of. Still, I would think that just sealing the doors with concrete and walking away would be pretty cheap, too.