Changing frequency would not necessarily mean an increase in coverage.
 Being able to utilize both sets of antenna sites might help fill in
"holes" and might add large areas, so in that way coverage could
increase.  Where they have licenses for both frequencies, they are
probably adding 800 MHz equipment to all their 1900 MHz antenna sites,
and 1900 MHz equipment to all their 800 MHz sites, there by maximizing
both coverage and capacity.

Not certain what they are doing, but whatever it is it is working great!
A few days ago I asked in the Cingular store in San Rafael as to their
frequencies and speaking with two reps they didn't know!  I do know that
it works fine in San Rafael, Fairfax, Woodacre, Lagunitas, Olema, Point
Reyes Station, Inverness and believe it or not even Camp Taylor.   I'm
using a Nokia 6250 900/1800/1900, and I tried the same route with a moto
850 plus I don't recall, but it was not a quad band. Prior to acquiring
AT&T Cingular did not work at all west of San Anselmo.  Obviously they
have now upgraded AT&T's towers, at least in this area.  Best you ask a
few Cingular customers -- friends or just walk into a few stores and ask
the customers.

Incidentally, it works fine with BT, but that is Nokia -- voice dialing
via BT is a great advent for me.   A few people have told me that during
peak hours they cannot make connection -- Cingular is becoming too
popular for their current abilities.  One lady told me that in talking
with Cingular in San Francisco that if someone is closer to the tower
than you, you can me thrown off, and they get on!

Miles