I really would doubt that you have any standing  - or ability - to be able to opt in to the plan at this stage of the game.  But I would take all the documentation that you have about the retirement to an attorney to review and to see if there can be established any nexus - an inkling of a connection - to the benefits packages offered weighed in conjunction with the benefits as they are paid out to you to presently to allow you to be able to take advantage of this other offering at this late stage of the game.  You need to see if the plan cuts you off forever from the ability to take advantage of new offerings.  I think that it might.  But good luck.