There was a non-Bell #5ESS switch being sold to the non-Bell Independent telcos back in the Bell System days (pre-divestiture).
I seem to remember that a company originally started by AT&T and GTE back when Ma Bell was in control of "The Phone System" named AGCS was "chartered" to manufacture and supply Bell System (designed) type products to the Independent Telcos throughout the country. The reason for this joint effort was that one of the FCC ruling regarding Western Electric was that they could only supply product to the Bell companies.
So there were many ILEC's (as they were called later) who had an AGCS #5ESS (can't remember the exact series name) switch in their CO's which was an exact design feature for feature to the WECo #5ESS switch.
In these later years, Lucent took over AGCS from AT&T and finally "absorbed" it into the Lucent family. If you go to the AGCS web site
John Stahl Telecom/Data Consultant Aljon Enterprises