With the lack of a strong military government in Mexico and the nature of the intricate political system under the 80 years of PRI rule in the country, finding information about missing people in the process was only plausible after the loss of the PRI's political hegemony in Mexico and the political will of the new PAN government over the last 7 years.
Jose Miguel Vivanco of Human Rights Watch in this link discusses the advances, or lack thereof, of the Special Prosecutor's Office which was created under the Fox Administration to investigate the disappeared people during the 70's in Mexico. Recently the office formally closed when the government published its agreement A/317/06 in the federal official newspaper. With the end of the investigation, not a single conviction was produced and only limited progress was made in uncovering the fate of hundreds of people who were "disappeared".
In Argentina, Chile and Uruguay, while there have been many difficulties and conditions in prosecuting past disappearances and abuses, Vivanco suggests that: "Mexico must still find a way to meet its obligation to investigate and prosecute these cases." While prosecutions have never been an easy task in any country, progression has come with new democratic governments in those countries most greatly affected by "disappeared" in the 1970s. With the election of another PAN government in Mexico, there must be some reconciliation in Mexico for the 600 missing people.