I had digital VoIP phone through brighthouse. Each phone requires it's own modem and that requires in turn electrical power so when my power went out? So did the phones. The upside to basic old school telephone systems is THEY have their own power sources and when power goes down on the lines? The phones stay up.
Not to mention at the time I had to pay an additional 9.95 a year to a service that called 911 for me when I called 911. They've changed this in a few areas, but from what I have heard largely 911 systems still don't support tracing of VoIP phone systems and that's a real danger I won't risk anymore.
I looked into going entirely wireless through cell phones, and/or using cable but, as you point out, there are issues getting 911 service and in some cases there are also significant equipment or start up costs. Also while the costs were manageable for some introductory period these costs rise precipitously once the introductory period is over.
In the end a simple hardwired telephone line and prepaid cell phone was the way to go.
Everyone here probably knows this but it should be mentioned that you don't need a cell phone provider to dial through to 911 on a cell phone even if you don't have a contract with a cell phone service provider. This means you can give a child or elderly person living alone a cell phone and as long as the phone is charged they can get through to 911 without having to carry any fees.
Without a service agreement they won't be able to dial any other numbers but being able to get through to 911 operators during an emergency is, in my book, a pretty significant advantage.