Yes, these iPads DO work in Brazil very very well, speeds are superb!
I am based between the two North East Cities named Recife and Joao Pessoa.
Where I live is relatively rural and is served by a local cellular transmitter provided by the TiM carrier about 2km away.
The SIM chip that I bought was a standard sized SIM that was cut-down to fit.
The Dealer, was an independent supplier non-official/registered TiM businessman. He sells SIM chips on the basis that you pay 1 year up front for Data only connections. You are prevented from making Outbound calls. If you do, he simply disconnects your SIM.
Being a non-Resident of Brazil, prevents me from taking out an official contract with any authorised Dealer, hence this workaround!
All-in-all I am immensely impressed and relieved that I have contact with the outside world considering that I live in a relatively rural area in the sticks of Brazil!