By the late 1970s, the Buenos Aires Underground had a vast array of ageing rolling stock - given that the different lines were developed by different companies in different periods - and the need for standardisation was becoming apparent given the increased cost of dealing with so many different models. One challenge was the use of 1100 V electrification on Line A and 1500 V on other lines, but also the use of third rail on Line B while all others use overhead lines. In 1978, Materfer presented a prototype vehicle which solved the issue of the different voltages by providing a model which could be easily switched between the two voltages, though Line B would remain an independent entity in the underground network. The trains were produced throughout the 1980s for use on Line E, however due to the economic problems in the country at the time, they never attained widespread use on the rest of the network since there was not the funding available to purchase new rolling stock for all the lines.
Current use
Over the years, the cars have seen cosmetic upgrades, as well as technical ones, such as the incorporation of Automatic Train Protection and ability to play pre-recorded messages through its speakers - which was unusually left out at the time of production. While the Fiat-Materfer trainsets briefly made up the entire rolling stock of Line E, today they find themselves on Line D and Line A as temporary rolling stock alongside newer trains while more new cars arrive. As the new rolling stock arrives for these lines, the Fiat-Materfer trains will be stored, then incorporated into Line E once again in time for its extension to Retiro station, though this has yet to be confirmed by SBASE or whether the purchase of new rolling stock for Line E would mean the complete retirement of the trains from service. On Line D they operate alongside Alstom Metropolis trains. The Alstom trains were originally intended to make up the entire rolling stock of the line and began operating in 2001, however due to the economic crisis in the country that year, only 80 of the 120 cars were bought for the line and the Fiat-Materfer trains were used to fill in the shortfall. In 2008, 14 more of these were eventually bought and incorporated into the line, while a further 24 are set to arrive between 2015 and 2016, meaning that the Fiat-Materfer cars will be retired from the line at that point. Similarly, the retirement of the La Brugeoise cars from Line A in 2013, as well as the presence of only 45 new CITIC-CNR cars at the time of retirement, meant that Fiat-Materfer cars needed to be incorporated into the line in order to make up shortfalls while the other 105 cars arrived from China. Ironically, the line had also been converted to 1500 volts that same year to incorporate the new CNR trains so the easy 1100 V to 1500 V conversion which the Fiat-Materfer cars were designed to have was ultimately never needed. The last of the CNR trains will arrive before 2017, and the Fiat-Materfer trains will then be retired from the line.
