User-specific routing... (Score 1)

The overview claims that in some cases an ISP will directly route user traffic through Carnivore. I would assume that this is mainly available in broadband cases (DSL, Cable) am I wrong? If it were only broadband customers who could be easily diverted through Carnivore, couldn't one just use the dial-in backup number that most brodband providers supply to ensure that individual e-mails are secured?