Reuters put out a story summarising how the pension plan deficit (not the obligations, just the deficit on the obligations) is bigger than the entire market value of the business.
How long can that last?
You can bet your sweet ass that BT are far from unique here. Are you relying on a company pension plan for your old age? (Or, even worse, just relying on the government to give you a State pension that will keep you in the style to which you have become accustomed... good luck with THAT!)
Review your pension arrangements, because if you're just trusting in others to deal with it all for you, then get ready for a big surprise when you can least afford it.