The state of Texas is about to sue Vonage. That's according to a report in the Dallas Morning News. One has to look at similar 911 incidents with cell phones and likely will find president.
While I'm very sensitive to the situation in Houston which occurred, this matter is a broader matter than that one instance, and the question becomes did Vonage do all they were supposed to do, promised to do and said they would do.
If my recollection is correct, Vonage offers users a 911 directing service tied to their address. My question here is did the family take advantage of that? If yes then the D.A. has reason to proceed. If no, then there may be some grounds for dismissal. I'm not a lawyer but at what point does not doing something or doing something that was made available determine fault or guilt.