[cisco-voip] Advice / Suggestions on large extension move?

[Dane]

We recently acquired a bunch of smaller offices and brough them into
our CallManager system.  We allowed them to keep their POTS lines and
their DID numbers at the times in each of the different offices.  This
created a big cluster within our cluster.  :-)  As we now had
extensions all over the place rather then within a nice simple range.

Anyway, I have finally recieved permission to begin cleaning this all
up.  First order of business was securing a new DID range in which I
will place them all in allowing for a simple and consistent flow or
group of numbers if you will.

I am not trying to figure out the best way to assign the new DID's and
therefore new four digit extensions to these offices.  Each office is
group in CallManager as a location.  I hope to do one location at a
time.

The biggest issue is I have to maintain a callforward or phantom
forward of their old extension for three months.  So basically I
configure someones phone with the new extension then have their old
extension forward to the new one.

I ask for advice and suggestions to see how others might handle this,
as this list contains some very knowledgeable indiviuals with some
great ideas regarding all things Cisco VoIP related and it amazes me
some of the suggestions and advice given here for things.  I often see
wonderful information on how to accomplish something, or even simply a
better way of doing the same thing some times.

I know their are ways to export all the phones say in a location to a
file and then manipulate the file and then import it, but I am not
sure how or if that is the ideal thing.

Any thoughts or suggestions would be greatly appreciate, trying to
automate or simplify the process as much as possible.

Regards,
Dane