AT&T's U-verse destroying Systems?

Even though I normally don't like to get in the middle of such things, I do understand the feelings that you have. Unfortunately, without knowing the Demark location and exactly the problem ATT techs had, it is hard to say. For 24 years I have installed telecommunication systems in businesses and homes. ATT has lost a lot of respect from myself and coworkers when it comes to typical residential or copper pair work. A lot of the original workforce was retired early and replaced with little or no experience techs that are trained on the job it appears.
With that said, they're responsible to provide the dial tone to the customers premise. One thing in businesses that I see all of the time is security techs do not follow tariff rules to stay on the customers side of a DeMark. The tariff states that the carrier has the right to disconnect service completely until it is resolved by whomever created the tariff violation. Normally, the ATT tech will just disconnect the violation and reconnect the line. It is not there responsibility to connect other companies equipment, normally that other company is called in after the installation to reconnect the equipment, properly.
Even though they went through the house doing a rewire, possibly do to problems they experienced, not sure, but it is up to ATT to inform the customer of the alarm disconnection and that's it. It is now the customers responsibility to contact the alarm company to reconnect it back in, hopefully using an RJ31X jack or similar wired properly on the customers side.