I have (as much as I hate to say it) had good luck with Time Warner phone and alarms. Since it is a "Managed VOIP Network" as opposed to just some VOIP add on done via your internet connection, it has been quite reliable where I am. Now, it is still prone to power outs, both at your gateway where you can assist by adding a UPS, and where you can't, at their amps and outside equipment it takes to get to you.
When I use TW phone, if at all possible, I still try to use a Line Seizure Loop by installing a BW1 adapter at the gateway. Which is even easier than installing it at the Telco NID. In this case you run your cat5 for the phone line (or 22/4 if you are using that) from the panel to where the gateway is, then the BW1 is plug and play at the 4 pin RJ on the gateway. This puts the alarm ahead of everything else, which is nice if TW cobbled in the wiring like they usually do (they have no clue about GOOD phone wiring) and used the existing NID outside to back feed the house from the gateway. Eliminates many what if's, including the original purpose of someone picking up an extension in the house to block the alarm dialer from getting dial tone (no loop).
