In a way it reminds me of how the North American Dialing Plan as structured in some major US metropolitan areas. What was once one Area Code has been divided into two or three Area Codes. But more recently, as especially cellular telephones increased demand for more phone numbers, they have geographically settled addition area codes on top of the existing codes, but have often restricted them to business numbers or cell phones only. So folks in a home may have one area code for their land line, but different area codes for cell phones in the same household, depending on when they were purchased and activated. Perhaps a crude comparison?

Occasionally, North Am orthodites have pointed to your province as a valid argument for the Anglican Communion to recognize the Anglican Church of North America as a constituent province of the AC, and an additional province to the national/regional/geographical provinces already in existence here.

The presence of two cathedrals in dioceses suggests the rule of thumb on one cathedral per diocese admits of anomalies.

The pertinent question re Waikato and Taranaki in NZ is whether it is seriously possible to maintain two egalitarian episcopacies in one diocese over the long-term. The current arrangements work well relationally because the two bishops enjoy working closely and harmoniously. Anyone care to predict how things will be in 2030?

Then there is the unique situation in the diocese of Los Angeles which designated a pro-cathedral last year. The Diocesan Center is housed in a building with a rather small worship space. So the diocese has designated a parish’s rather large, ornate building as a pro-cathedral where the diocese’s large liturgical functions are held. “Called by Bishop J. Jon Bruno to provide “one ministry in two locations,” the ProCathedral of St. John and the Cathedral Center of St. Paul offer daily opportunities for worship, education and service.”

In the United States, there are several instances in which a Roman Catholic diocese maintains two Episcopal See cities, each with their own cathedral or co-cathedral. Examples include the Cathedral of Saint Paul and the Basilica of Saint Mary in the Archdiocese of Saint Paul and Minneapolis (Minnesota) and St. Mary’s Cathedral Basilica and the Co-Cathedral of the Sacred Heart in the Archdiocese of Galveston-Houston (Texas).
Other instances include the Diocese of Altoona-Johnstown (Pennsylvania), the Diocese of Fort Wayne-South Bend (Indiana), the Diocese of Great Falls-Billings (Montana), the Diocese of Houma-Thibodaux (Louisiana), the Diocese of Kansas City-Saint Joseph (Missouri), the Diocese of Pensacola-Tallahassee (Florida), the Diocese of Springfield-Cape Girardeau (Illinois), and the Diocese of Wheeling-Charleston (West Virginia).
There are also three instances in the United States in which a cathedral and its co-cathedral are in the same city. This usually occurs when a historically important cathedral becomes too small to serve a growing population, and a larger co-cathedral is constructed to accommodate larger services. Examples include:
The Cathedral of Our Lady of Peace and the Co-Cathedral of Saint Theresa of the Child Jesus, both within walking distance of each other in the Diocese of Honolulu (Hawaii).
The Cathedral of the Immaculate Conception and St Joseph’s Co-Cathedral in the Diocese of Burlington (Vermont).
The Cathedral of Mary Our Queen and the Basilica of the National Shrine of the Assumption of the Blessed Virgin Mary in the Archdiocese of Baltimore (Maryland).

In the Episcopal Church, both the Diocese of Iowa and the Diocese of Minnesota each have two cathedrals, both located in different cities; however, they are not styled “co-cathedrals.”

Perhaps we can say that when a diocese is spread out, or named after two cities, it becomes necessary to have two cathedrals?

In the (Anglican) Diocese of Sydney there are two ‘cathedrals’ that have no actual diocese attached to them: St John’s at Paramatta and St Michael’s at Woolongong. The bishops ‘of’ both places are not diocesan bishops, but regional bishops of the Diocese of Sydney.