The IFATCA apparently has some "inside" information that has not previously been released from official sources. This information tracks with my earlier posts...and those of others... that 600XL was never cleared to any level other than 370, the altitude at which the collision occurred.
The question then for the crew of that aircraft is "should they have descended to a different level(360) on their own volition"" after passing BRS. The answer to that question appears to be founded solely in the lost communications regulations. While not having information as to whether Brazil has an exception to ICAO(differences), the ICAO requirement is quite clear. After the aircraft becomes aware that it is in a lost comm situation it must squawk 7600 while maintaining previously cleared course and altitude for 7 minutes and then maintain flight planned parameters. The seven minute window starts with the selection of code 7600(and is obviously intended to give ATC time to make necessary adjustments to other aircraft given the impending change, in altitude, for example, by the NORDO aircraft). In this case, the data indicates 600XL attempted several calls to ATC and after a few calls heard a transmission from ATC directed to it which was partially unreadable. It then attemted several more transmissions to clarify frequency change instructions which apparently were not heard by ATC. The collision occurred 3 minutes later. Whether the timing of the ATC call was serendipitous or in response to hearing the call from 600XL is not clear. It is also not clear whether the 600XL crew had come to the definitive conclusion that a lost comm situation existed but even if it had at this point 3 minutes prior to impact, the rules would have had it maintain 370 until a time well past the actual time of impact.
While the IFATCA statement and comments delineate the possibility of long standing ATC problems with equipment implementations and communications coverage and, further that the controller on duty may have been improperly briefed(believing that flight was at 360) when coming on duty, ATC procedures should have caught the fact that the last confirmed altitude (370)of 600XL verbally occurred just prior to crossing BRS (why wasn't flight instructed to maintain 360 after crossing BRS which was to occur literally in a few minutes ?) with mode C/S altitude reporting being available and showing 370 for some 40 miles after passing BRS. The apparent display of a calculated level of 360 not withstanding, should not the Gol flight have been advised of opposite direction traffic at 360 unconfirmed and NORDO..... if not given a separation vector or climb instructions?
As to equipment failures or poor man/machine interfaces or inadvertent improper operation of equipmnent(none have been eliminated as contributing factors), the ICAO Rules and ATC procedures are(should be) designed to be fail-safe and provide proper alerts/actions to prevent such occurrences.
Also, there has been no mention of the communications with the Gol flight during this period. Had they been on same frequency as 600XL would not they have heard its calls to ATC which (with good phraseology and use) may have included level /position information in its transmissions? Since it is likely that they were not, should there be a procedure/practice in remote areas with possibly less than adequate communications which would assure that aircraft approaching each other at a closure rate of M1.7 would be monitoring the approaching sector frequency if a common frequency is not in use (so that the a/c crews would be aware of other traffic)?