Or instead there ought to be a simple way to just opt in. Or they could produce a FF/IE addon. Or put a big notice on their homepage with this info. Or automated social media notifications. Etc.
Messing with DNS to redirect bad domains to ad parking pages is still around but no one cares anymore. However, this is right in the user's face which feels different, like it's an offensive volley, like one ISP is finally ready for war. The first battle in ISPs training users to accept a tainted connection.
In all honesty, I think they picked the perfect application to start the ball rolling. Few average Joe customers would argue against email outage notifications because it seems like it's an important function that the ISP should provide. More importantly users are used to dynamic pages now, it "feels" like a Facebook or Twitter thing. So in their mind it's probably ok, or at least something that would be hard to argue against from a layman's perspective.
So it's a good starting point to start boiling the frog. I'll bet that their internal calculations show no more than one year to completely boil the poor beast (i.e. ad insertions). That's the holy grail.