I'd like to echo the thanks for making the debut of NBC NIS available because as a long-time collector of old radio news, this was something I was really unfamiliar with and now that I've had a chance to listen to what it was all about, I think it was a concept that deserved to last longer than it did. I've been able to sample a large number of other network radio newscasts from this era through pastdaily.com and by contrast the CBS World News Roundup broadcasts have a much stodgier quality to them presentation wise compared to the approach NBC was trying.
As a result I've been looking about for the other examples of NIS to be found on the net and this is what I've come up with:
January 23, 1976. WWTC Minneapolis
http://www.radiotapes.com/WWTC.html
August 11, 1976. WNIS-FM Chicago
http://chicagoradioandmedia.com/multimedia/audio/6756-wnis-fm-newscast-august-11-1976
December 31, 1976. WWNS-FM New York
http://formatchange.com/wnws-fm-becomes-y97-wyny/ (the final minute before the format change and the end of NIS in New York)
January 7, 1977. WEAN-Providence, RI.
http://northeastairchecks.com/checks/wean.ram
February 27, 1977. WNNS-FM, Louisville
http://www.lkyradio.com/WAMZ.htm
Let's hope there are other examples to be found! But in the meantime, these initial three hours was pure gold.