Since the iPhones 6s and 6s Plus were launched, a debt hung in the air for Brazilians interested in buying them in the United States: which model will be the one approved by the National Telecommunications Agency? This is very important because Apple Brasil only supports the approved models.
As this Apple LTE page indicates, there are two models of each size being marketed in the USA: A1633 and A1688 for iPhone 6s, A1634 and A1687 for iPhone 6s Plus. The first of each are those of the operator AT&T and several other regional ones; the second, from Sprint, T-Mobile and Verizon. From last year to this model / operator structure has changed a lot, so it was difficult to guess which one would be approved.
Today, however, MacMagazine discovered a detail that practically confirms that the iPhones 6s / 6s Plus sent to Brazil are the same as those of T-Mobile A1688 (iPhone 6s) and A1687 (iPhone 6s Plus), therefore. Inside of General Adjustments About Legal Regulation of these devices, Anatel's seal and even its homologation numbers already appear: 3457-15-1993 and 3456-15-1993, respectively.
Homologation certificates have not yet been painted on Anatel systems, but it is normal that they will only be published a few weeks later. It is worth noting that the same stamps * do not * appear on iPhones 6s / 6s Plus purchased via AT&T, so the indication is quite strong.
Apart from the warranty issue, all iPhones 6s / 6s Plus work perfectly on the Brazilian 4G (LTE).
(tip from Daniel Lunelli)