It probably depends on what telco you have and how advanced their switching system is.
I am with MTS/Allstream in Winnipeg Canada and there is no problem moving telephone numbers between the 60 or so different exchanges in the 14 central offices if I move. And I think that is has been like this for the last 5 years if not longer.
In fact MTS will ask if you want to keep your existing number when you call in to change your address.
As well I could also move a single line telephone number to / from Shaw Cable telephone service in Winnipeg to MTS if I want to change providers.
And in March of this year the CRTC (Canadian version of FCC) is allowing single line numbers to be ported to and from all communication vendors (cell phone, telephone co's, and cable co's)in the local serving area.
This number portability as stated in the post above will now make it harder to know what part of they city you are calling.
