As pax mentioned, you have issues with the plan being terminated at all. Read Rev. Rul. 89-87 and note that plan assets generally must be distributed within one year of the termination date. Extensions are considered for reasonable delay, but 6+ years!? If the IRS does consider the plan not terminated, you have a whole host of issues like the need for actuarial valuations and potential contributions since the termination (and I use that term loosely) and the need to update the plan document for law changes. I seriously hope the benefits were frozen along with the termination or you could also have additional accruals. If the plan was TH, you definitely have additional accruals.
Now as for amending for GATT, while technically there's an anti-cutback exemption, I think you have issues because the benefits were probably not paid out timely. A participant could raise issue with an amendment now that reduces a lump sum that should have been paid years ago.
QUOTE
I am not sure that the failure to distribute assets voids the accrued benefits payable on the date of termination because the cut back rule prevents a reduction in the accrued benefit because of a plan amendment.
The accrued benefits are definitely not reduced.