See this article shared by Claire Rubin, Why Uber Can Find You but 911 Can't, which appeared in the Wall Street Journal. You might need a subscription to read the entire piece.
While the tech companies work to have a solution that functions for their networks and smart phones, there is another problem. All the 911 centers across the United States will need to be able to import that information and dispatch first responders accordingly. While there are four primary cellphone companies working on their side of the tech issue, there are approximately 5,800 public safety answering points (PSAPs) scattered across the nation.
These are protected as fiefdoms of county sheriffs and others who would have total control, rather than the most up-to-date technologies in their centers. Enhanced 911, which is to provide the location identification for wired phones and dates back to the early 1990s still isn't everywhere. Let alone all PSAPs having the location identification from cellphones.
Uber and their likes are national companies built on technology. Until we invest the money in our 911 systems to give them a technological focus, we will seriously lag the commercial advancements in location technologies that are being made every day.