Wonderful shots! Is the Midi a privately owned railroad? I know that Great Britain privatized some (or all?) of its rail network, but I'm ignorant of what other European nations have done.
Before the days of SNCF, which came into being in 1938, the railways in France consisted of 6 major companies which were situated more or less on a geographical basis. The Midi company was situated in the South West, around the cities of Bordeaux and Toulouse and taking in the whole border with Spain. As it had a number of lines in the Pyrenees which had steep gradients, it was one of the early companies to electrify many of its lines, using 1500V DC. In 1936 it merged with PO, (Paris-Orleans), its neighbour to the north. It had one line, especially suited for high speed, between Bordeaux and Spain and this is the site of the World record for electric locos of 331kmph. It used very elegant arched supports for the catenary which have been replaced in various places as they were unsuited to modern needs but several branch lines still have them. Hope this helps.
PS, the shot on the viaduct is incredibly difficult to get as it is only accessible by boat. The viaduct sits alongside the aqueduct on the Marne-Rine canal.