First, to explain a bit, BISP stood for Business Information System Programs (or something like that), and referred to a part of Bell Labs at Piscataway that was originally staffed by Telephone Company personnel, for the purpose of writing software for use by the Companies. The idea is that they would send people on temporary assignment, they would code up the programs, and then return home, job done.
When I got to Bell Labs, in 1970 the operation was alive, but by 1972 it was obvious that it was a failure, so the organization was grafted onto Bell Labs (department numbers 9xxx), the temporaries were sent home, and Bell Labs people were moved in or hired. That gave me a great opportunity, so I transferred there. Vic Vyssotsky, a real blue-blood Bell Labs guy, went over to run it. My department head was Rudd Canaday, another genuine Bell Labs guy.
That's where I did SCCS.
I'm almost sure that SCCS/PWB refers to SCCS, not to the OS. By the time of this memo (1977) I was long-gone from SCCS, and was working under Rudd on a new system to produce telephone directories.
--Marc