I was surplused a year ago and here is what I found.
MR75
Age 50yrs + Time in service 25yrs
Age 55yrs + Time in service 20yrs
There is another for 60yrs old....I think it was 60yrs + 10yrs
Upon surplus they allowed me to give up 50% severance to get 2yr credit on either set of years.
Med/Dent Subsidize
I was hired into Ameritech and you only get Med/Dent Subsidization if hired prior to Aug 1st 1997.
Pension
Maxes out when you hit MR75 years.
Giving up 50% severance has no impact.
Overall if you are not working for AT&T until you hit MR75 you don't get full max pension. (I lost 50%)
Call benefits people and ask for specific details applicable to you. Don't trust what others tell you.