Thanks Ndavies, I suspected something was missing. So this agreement between GM, Delphi, and the PBGC was forced upon GM or was it voluntary on GM's part? And this had to be approved by the judge?

From the article:
G.M. issued a statement on Tuesday [July 21] saying that it would “top up” the pension benefits for those in the union whose payments could be shrunk to the government limit. The statement cited the agreement G.M. negotiated with the union in 1999, in which the automaker had promised not just to pay a supplement but in fact to take back the union pension plan if Delphi could not run it.

“As with other union agreements that it has assumed from the old G.M., General Motors Company will honor those commitments,” the company said in its statement.