( PSAP = Public Safety Answerin Position = the 911 center )
[ lots snipped ]If you're a registered PSAP you can get the local telco to provide you with the Caller ID info, even if blocked.
Keep in mind that the caller id number is passed all the way from your local central office to the destination CO. It's only at that last location, immediately preceeding the "final loop", that the number is replaced with a "not available" notation.
So if you're approved, the final CO will, indeed, pass it along.
Similarly, if you've got a facility that's considered, for want of a better term, "close enough", you can get the same exemption. For example, back in 2001 a group of universities and hospitals called "Insight 100" (since many of them used the Northern Telecom switch of the same name) requested this from the FCC so they could better assist callers to their emergency rooms.
(FCC Docket 91-281, file # NSD-L-01-153)
After the usual bit of paperwork delay (not too bad, considering), and a bunch of comments from the public (including me), the FCC granted them this waiver.
Other groups that are covered would be (in many areas of the country) your local volunteer ambulance or fire company, many of which are reached through a direct-dial seven (ten) digit call.
And yes, CNID is not as reliable as the more specific 911 database, but it's far better than nothing.
_____________________________________________________ Knowledge may be power, but communications is the key snipped-for-privacy@panix.com [to foil spammers, my address has been double rot-13 encoded]