PG&E does not call people regarding this program.  You are correct.  They do however authorize contractors to implement the program for you, and provide those contractors with your information.  The program does not cost anything, but you have to fall below a certain income to qualify.  If you do, you get free energy improvements to your home, and a discount on your energy bill.  They are merely calling to see if you qualify.  I did not qualify, but I did pry.  I found it was a legitimate company, and a legitimate program.  They are even listed on the PG&E website, as well as other companies who are authorized to do this program.  Instead of making assumptions, ask them where you can verify they are legitimate.  If they are listed on the website then they are good, if not then it might be a scam.

This number left a 44 second message that played music and a recording saying "thank you for holding, we look forward to talking with you soon, please hold the line and we'll be right back with you".

They started calling me yesterday.  15 different numbers!  I actually scream at one of them to remove me from their damned list.  They supposedly found my resume on Monster and are calling about some contract job in a state that I don't even live in!