They were back in the day, to AT&T, THE SYSTEM..! You'll see a few here and there, but many went away with the onset of localized voicemail .. These didn't have the ability to support local vmail systems typically. Yeah, one was made for them, but I saw 1 of them for every hundred classic systems I saw..
Still, they are solid, but they are so old now, I wouldn't trust the power supplies in them., they just gotta be Tired!
As Cheap as they may be, the same phones will work on it's bigger brother the Legend... Those processors & cards have been around a long time to, but many are available, they refurb them, and you'll get a much more robust feature set.
Step up a Decade or so!!
MrTelecom1
Re-Living the AT&T/Lucent/Avaya issues since 1979!