I was on a call that included one of the VP's in HR, there is a lot of bad info out there, the whole process is very simple, they were quite clear on what the options were.
There are 3 (4) possibilities you can be notified of:
1) you are told you are being laid off.
2) you are being retained by the company.
3a) you get an assessment and then end up being retained.
3b) you get an assessment and are then told you are being laid off.
You are not eligible for severance with 2 and 3a since you are keeping your job.
You are eligible for severance with 1 and 3b as the company is letting you go.
If you are in the 1 and 3b group you can if you want apply to open jobs, but you are under no obligation to apply for open jobs.
You cannot be assigned a different job, you either keep your job or you lose your job.
Severance is 2 weeks for every full year completed, if your layoff date is 1 week before you would reach another year of service you are out an additional 2 weeks of severance.