OK since nobody has answered the question.
AT&T has policy in place to determine retirement eligibility. This may or may not apply to all employees, based on the company they were originally hired. If you are over age 50 and your age plus the number of years of service based on your NCS date, is equal or greater than 75, you may be eligibile for retiree benefits, which may include medical insurance, product discounts, and ability to draw on a pension. There are several who get no benefit as part of the agreement when AT&T bought that company, like AT&T Wireless. Also bargaining agreements also hold provisions for retirement and benefits, depending on agreement, which I believe are only the old agreements for all the old landline company's . Non of the wireless agreement have any retirement articles.
This policy was put together something long before the 1984 breakup of Ma Bell,and was just carried forward by the companies split off from AT&T.
IN relaity to get the best benefit you would have to have been hired under an SBC, Bellsouth, Ameritech, Pac Bell, and legacy AT&T. Anyone who came from someone that was bought, like AT&T Wireless, IBM may not get anything.