Surprisingly enough, I had at one point hoped to practice Pension Law and had the opportunity to participate in the wind-up of a big US pension plan (Anaconda Copper). The notice provisions were strict, even to the point of requiring people to be tracked down like long lost heirs and annuities bought in trust for those that could not be found. I have also seen cases where Notice means personal delivery or regular mail to each person entitled to receive the notice with provisions to apply for authorization to give notice through public advertisement or otherwise if they could not be found. I am not sure which procedures apply here. The Rules I have seen that seem to apply here are not that helpful as it is probably more defined in case law. The Rules of Notice may be found here.