hogtied,
I went through something similar to this twice, and observed another buyout within megcorp before that. What you get all depends...
I watched an entire design department terminated because a new GM felt it was too expensive.
I never did understand the logic of getting rid of the most knowledgeable engineers in the division, those who design the future products, to save a few dollars today. The GM later was terminated after a buyout. Anyway, at least some of those engineers were given what amounted to one year's salary bonus to "sign the forms" and move on. The most talented immediately found new jobs.
I had a different experience. Twice the plants I worked in were closed. The first was after the previously mentioned buyout by a competitor. I was given the option of a retention bonus if I'd hang around and facilitate the closing and transfer of products. I had nothing else to do, so I agreed. I received enough money for a down payment to purchase two rental properties, around four months take home salary. Had to take out a small 2nd on another rental to close the house deals. The day after I locked the door I left for Hawaii for two weeks. While there, I received an offer to work for a sister plant. Never missed a beat.
Fast forward four years. Dot com bust in process. Now working in a second sister plant doing the same thing as in first plant. We're notified the plant will be closed in six months. Incredibly, I received the same offer: help close the plant, received retention bonus. This one was even better, 6-months salary which was based on years of service. Even though I knew that one group got 12-months, it was a smaller group and a different management, and I couldn't get them to budge. I did negotiate with them to allow me to stay until I was 55, an extra two months, so I could qualify for and receive retirement medical and make 401K withdrawals penalty-free if needed. I didn't, but I wanted the additional peace of mind. Things were looking pretty good until 9/11 occurred. That changed the whole employment picture. But that's another story.
Hope you get the chance for a little extra kicker going out the door, if that's where you're headed anyway.