This announcement is limited to calling from Gmail (which I guess covers people using an OBi, for example). What about people who don't have internet access at home and make long-distance calls from an ordinary phone (by dialing their GV number)?
Edit: Should add that the 2011 announcement
»gmailblog.blogspot.com/2011/12/f ··· ada.html
simply said "we've extended free domestic calls within the US and Canada for 2012". The 2012 announcement
»gmailblog.blogspot.com/2012/12/f ··· ada.html
seems to be specific to Gmail (especially since it's not on the GV blog).