And just to clarify fo those who don't know, or might be under typical misconceptions...
"Rate Center" is not the same as "Wire Center".
A Rate Center is a "legal" item, something defined by tariff indicating a region where everything (usually) has the same BILLING or RATING criteria. It is NOT (necessarily) the same thing as a "switch coverage" area, i.e., the region covered by a central office *SWITCH* aka "Wire Center", these latter terms being more "technical" or "network", rather than "legal" or "regulatory" (billing and rating).
Something else to remember or consider...
IIRC, the FCC/etc. only requires that (intra-landline) portability be provided if you want to change telcos/carriers, while still remaining in the same rate center.
(BTW, a central office switch or wire center can can serve customers in multiple rate center areas. Most CLECs are set up like this even in dense metro areas. There have to be dedicated (NPA)NXX office codes for each rate center though, even though all customers could be served off the same switch).
Most telcos will allow (or are "supposed" to allow) you to port your service including number between each other as long as the same rate center is involved. While there is no "technical" or "network" problem involved (in most cases), if you want to port your number because of a physical move, BETWEEN central office*switches* in the same community, and stay with the same incumbent local telco as well (the "Bell" or "independent"), if you are in a large city (and sometimes smaller town in some cases) where there are MULTIPLE central office switches...
SOME telcos *DO* allow this, OTHER telcos (normally) either do NOT allow this, or else put up roadblocks to discourage you from doing this. In the long run, it would be to that ILEC's advantage to PERMIT this type of port, but some telcos just don't allow this (unless you probably threaten to go to regulatory, or else go higher-up within the telco complaining to the right people in the right department/etc).
Bell Canada and BellSouth (now at&t) are known to usually NOT allow such intra-company geographic ports which, while still in the same rate center, would be a physical move between serving central office switches.
Qwest (formerly US West) Embarq (formerly Sprint, at least Centel in Las Vegas) have been known to allow such intra-company geograhic ports within the rate center between central offices due to a physical move.
One *COULD* migrate from the ILEC to some CLEC such as the cable-TV company's telco, prior to the geographic move. Then, when moving their household across town, tell Cable-TV's phone company about the move. Most CLECs have only ONE switch serving huge geographic territries, even in large metro areas. As long as one doesn't cross rate center boundaries with their physical move, the CLEC will allow one to keep the same telephone number. After a year or two following the move, the incumbent telco will have already started sending mail-outs and maybe even "telemarketing", as part of a "win-back" -- where they want you to "port back" to them!
And since you did NOT move/port across rate center boundaries, they will HAVE to allow you to return to them with your original number that you ported-out when changing to the CLEC, even though you are now living in a different ILEC's central office switching region than you were prior to your move! And you will be served from that "new" (different) ILEC's switching office as well in your new neighberhood if you do agree to "port back".
If that's the case, WHY couldn't that ILEC simply allow you to port your number between their switches (still within the same rate center), when you had to make that geogaphic move a year earlier!? It would have meant better customer relations/impressions, and it would have been easier/simpler for telco in the short and long runs! IMO, the FCC and CRTC should have REQUIRED such ports as well, from the very beginning!
One known reason for NOT allowing such ports, and not so much a "technical" issue, but rather a "jurisdictional" or "numbering" issue, happened to US West (now Qwest) in "Twin Cities Metro" MN, and in the Phoenix AZ Metro areas, in the later 1990s.
Remember that Qwest (US West) usually DOES allow intra-company, inter-switch, still intra rate center ports, unlike Bell Canada and BellSouth. However, the Minn/St.Paul area code splits of the later 1990s, as well as the Phoenix AZ area code split of 1999, were based on poliiical jurisdictional boundaries, and NOT on telco rate center boundaries (there were other similar area code splits of the later 1990s as well).
With such splits in those two US West metro areas, if one ported their number, they might have ported across the new area code boundary. And state regulatory did not want this happening! US West had to prevent such ports. However, CLECs (and wireless) existed with the same NXX office codes (and single switch) regardless of geography (although within the same rate center). There was somewhat of a nightmare in both cities as to determining which area code certain CLEC and wireless customers fell in due to the split. The splits in both places (and other cities where such political jurisdictional splits happened which did not follow telco rate center boundaries) were rather MESSY area code splits! Also, in both cases, Minneapolis/St.Paul and Phoenix Metro, US West requested an overlay, but regulatory ordered the splits, and those rather messy splits as well.