I've just returned from a week in Japan, and brought my Verizon phone with
me to see if CDMA roaming now works in Japan as advertised.
CDMA roaming does work. Whoo-hoo!
However, it only works in Narita (international airport) and metropolitan
Tokyo. It did not work on the outskirts of Tokyo (e.g., Higashi Kurume),
nor in Yokohama or Kawasaki. One of my friends has KDDI au (Verizon's CDMA
roaming partner in Japan, pronounced as the letters "a u") and her phone
was showing a strong signal at the same time I got "No Service".
It's 1x, not EV-DO, which is strange since KDDI is a very competitive
company (#2 in Japan) and both #1 and #2 are 3G (UMTS).
Historically, KDDI used a variation of CDMA with different channel
assignments in the 850 band from other CDMA countries. KDDI recently
decided to play ball with the rest of the CDMA world (after intentionally
not playing ball for many years) but of course they have to support their
existing phones.
My surmise is that the towers in Tokyo and Narita operate in either mode,
but elsewhere the towers have not been upgraded yet. Some of KDDI's phones
operate in either mode as well.
Although CDMA roaming is cheaper, I would not recommend depending upon it
unless you are only going to be in Tokyo. When even major cities such as
Yokohama and Kawasaki are not yet online, the world-compatible CDMA
service in Japan should be considered embyronic.
UMTS (the 3G form of GSM; there is no 2G GSM in Japan) roaming with a
Verizon (actually, Vodafone NL assigned to Verizon) SIM card is available
in far more areas. It looks like Verizon prefers SoftBank, whereas AT&T
seems to go with either SoftBank or NTT DoCoMo.
So, I took my SIM out and put it in an unlocked UMTS phone to use when I
was outside Tokyo, then in Tokyo switched to CDMA. I have no idea what
would happen if both phones were online simultaneously, and didn't care to
try.
The BlackBerry Storm supposedly supports UMTS in the 2100 band that Japan
uses, so you ought to be able to use it seamlessly in either CDMA or
GSM/UMTS mode throughout Japan.
I have a Storm now, but at the time I was roaming with my Motorola Z6c
which yesterday after I had returned from Japan had a confrontation with
spilled fluid...and lost. Hence the Storm, and I'm not NE2 eligible so
had to pay full price...
-- Mark --
http://panda.com/mrc
Democracy is two wolves and a sheep deciding what to eat for lunch.
Liberty is a well-armed sheep contesting the vote.
CONFIRMED: CDMA roaming works in Japan. 
Linear Mode
