A voice recording, made by a person who doesn't identify itself, and doesn't know my name, called to say the IRS was filing a lawsuit against me and I should urgently call a 1-600 number. The IRS does not operate this way!
It appears this is a generic phone number related to Project Fi. The number itself doesn't belong to any one spammer or scammer. Instead, it shows up because of the way that Fi works. Project Fi is built on Google Phone/Hangouts technology, which allowed you to establish a phone number on your Google account and have calls to it forwarded to any number of devices. Fi switches between wi-fi, Sprint, T-Mobile, and US Cellular, depending on which network it determines is fastest and most reliable at the time. When you're on wi-fi, you're basically using Google Phone. When you're on one of the cell networks, though, your phone is basically being forwarded through an invisible telephone number unique to that network. Most of the time, you'd never know this is happening. But those invisible numbers are actual, working phone numbers, which means that autodialers and the ANI system (automatic number identifier) can see them. If someone tries to call one of those invisible numbers, the call gets sent from that invisible number to the Google Phone system, which then forwards it to you, but the Caller ID sees it coming from this generic Google forwarding number instead of the original caller.
This might be more common with callers who block their caller ID or set it to private. Google passes through the caller ID of a call you receive so it shows the original caller instead of whatever Google phone node is forwarding the call to you. It might be that when there's no caller ID from the original caller for Google to pass through, the forwarding node's caller ID shows instead. Blocked caller IDs seem to show private or blocked when they are direct to your Google number, but not when they go through one of these "invisible" numbers.
That would explain why some people have seen this number related to 911 calls. The system that 911 uses to see what number you're calling from is similar to the ones that corporations, telemarketers, debt collectors, and scammers use - except that it sees a bit more information, like what cell tower your call is going through and sometimes your approximate GPS location. If that system sees one of the invisible numbers instead of your Google number, that's the number the operator will dial if they try to call you back. Police departments and 911 centers usually have their numbers set to private. So, either because the 911 operator dialed back one of the "invisible" numbers, used a private extension to call, or both, you end up getting a call from the operator that shows a generic Google forwarding caller ID.
There was a post on one of the Project Fi support forums from a 911 operator that actually tested this. They made a controlled test call to 911 and checked what source number the 911 system showed, and it was different than their Google-assigned number. Then they switched cell networks and made another call, and it showed yet another number. That showed that a Fi phone uses different phone numbers for different networks. Then they called back on the numbers shown by the 911 system, and the calls rang through to the Fi phone but showed the generic Google forwarding number. But I don't think they ever tried calling with their caller ID unblocked, so they didn't determine whether it only happened to blocked numbers or if it happened whenever an "invisible" number was called.
A voice recording, made by a person who doesn't identify itself, and doesn't know my name, called to say the IRS was filing a lawsuit against me and I should urgently call a 1-600 number. The IRS does not operate this way!