Apple:

iPhone users in the United States who call 911 will be able to automatically and securely share their location data with first responders beginning later this year with iOS 12, providing faster and more accurate information to help reduce emergency response times.

The way it works, prior to iOS 12:

To address this challenge, Apple launched HELO (Hybridized Emergency Location) in 2015, which estimates a mobile 911 caller’s location using cell towers and on-device data sources like GPS and WiFi Access Points.

And the new process:

Apple today announced it will also use emergency technology company RapidSOS’s Internet Protocol-based data pipeline to quickly and securely share HELO location data with 911 centers, improving response time when lives and property are at risk. RapidSOS’s system will deliver the emergency location data of iOS users by integrating with many 911 centers’ existing software, which rely on industry-standard protocols.

And:

The FCC requires carriers to locate callers to within 50 meters at least 80 percent of the time by 2021. iOS location services are capable of exceeding this requirement today, even in challenging, dense, urban environments. This new feature allows Apple to make these benefits available to local 911 centers now rather than years from now.

Not sure of the details, but sounds like a more direct, efficient process, yielding more accurate locations well ahead of the FCC required date.