When this happened at a company I worked at, the line from management was, "Stay for two months and train this person and your severance is 6 months' salary. Don't train them and you leave in five minutes with 6 weeks' severance."
A friend of mine was in this position. It was a requirement for her to get severance, as degrading and awful as it was.
Yeah it's either train and get severance or leave now. However, IBM just reduced the severance from 2 weeks per year of tenure to a standard 1 month. At that point I'm not sure it even matters.