[Gordonjcp]

You wouldn't necessarily make it (easily) publically available.

When someone dials 999 in the UK, the call goes to the 999 handling centre where it's directed on to the appropriate agency (Police, Fire and Rescue, Ambulance, Coastguard etc - often one will pick it up and then bring the rest). Both the 999 receiving centre and the agency that the call is handed off to get the location of the caller, but only if it came in via a 999 line, got handed over via a "999 to agency" line, and then over a special dedicated connection that you most definitely do not have.

I'd expect that for something like self-driving cars it'd use the opposite of "Greenwave" which will adjust green light timings on routes to suit emergency vehicles. I know that city buses where I used to live also had Greenwave and would update their control room with their GPS position, which would then "nudge" traffic light timing to speed them up or slow them down so they ran to schedule.