To this article's credit, ADT when counter-advertising people thinking about leaving (source: me everytime they raise their price on my aged featureless system) is that alarms made on a cellular signal instead of a land line can be jammed with 75 dollar cell phone signal jammers.
They stand on the bedrock that their existing systems can't be manipulated like that. While this article makes it clear that this is not a cheap or unsophisticated hack, depending on the value of what you have in your home this kind of hack can very much be worth the price of admission especially when free and explained on the internet.
That's why relying on a single link for anything is a bad idea - if a system is known to use a landline, it's trivial, especially as in most parts of the US phone lines are aboveground, to cut the phone line before breaking in.
They stand on the bedrock that their existing systems can't be manipulated like that. While this article makes it clear that this is not a cheap or unsophisticated hack, depending on the value of what you have in your home this kind of hack can very much be worth the price of admission especially when free and explained on the internet.