Hmmm.. strange, I found this while looking at some plans:

http://www.timnordeste.com.br/asp/roaming/roaming_alianza.asp

    It looks like a lot of other South American countries are using
1900 too, thought the US was about the only place using 1900.  According
to www.gsmworld.com some of these same places are using 850 too.  I
realize 3G isn't GSM compatible, but curious, what frequency is it using
and is it standard across the globe?  If so, that would be amazing that
everyone finally agreed on a single universal frequency, somehow I doubt
it.

    I believe you're right on the long distance thing, according to
this you should pre-pend 41 (of course, the code for TIM, and they claim
you'll get the best rates, for their benefit I'm sure):

http://www.timnordeste.com.br/asp/roaming/nacional/gsm_comofazer.asp

    I wonder how they charge the call if you pre-pend a different
long distance carrier while initiating it on their network/service plan.
Also, apparently, from what I've read, it seems if you're in another
state you might not only be paying roaming charges to the network you're
on, but also the long distance for the leg of the call from your local
area (i.e. where your phone number is) to wherever you are.  Sounds like
a rape job to me, kind of like the people who get charged for every leg
of a GSM call when roaming internationally and the call diverts to
voicemail due to "no answer" or "busy".