The only thing you can do to prevent non-reporting of phone-cut
attacks is to have backup reporting VIA cellular or long-range radio.
The growing trend will be IP based monitoring over your high-speed
Internet, but that is not considered a viable residential application
(yet).

So how is high speed internet going to be any better when you can cut that
physical wire just as easily as any telephone line?

People's internet connections are frequently always-on, so that
"monitored" means what, apparently, a monitored phone line
doesn't anymore. To whit: The monitoring system can ping
your alarm system every minute or so, and if it doesn't
get an answer, freak. I recommend not using anything created
by microsoft in such a system.

--Goedjn