The only Lucent or AT&T "Non KSU" sets with
intercom that I know of are 4 line. The 955
and the 964 with answer machine and auto attendant.
Be careful though as your limited to the total amount of wiring when you use these phones.
IBM has their IBM-412CId which is about the same thing, it's also 4 lines as well as the
Uniden UB-410
If your interested only in AT&T you may want to check out this link.
https://www.telephones.att.com/ Good Luck