I don't think a free unlimited dialup account is necessary. A payg dialup is possible, and this is available to people who are on BB, infact i have one myself. to sign up for one, just go to
https://autoreg.autoregister.net .
At the end of the day, the broadband packages are for residential use, so people should be able to survive for the time of an outage without their connection. Ok, so you could argue that some people experience a lot of problems, but the vast majority of these complain and get money back for the time without service so IMHO implementing a free dial up for backup is not necessary.