In my current savegame, my network serves the whole map though some cities are still isolated, mostly in the south-western part of the map.
The general layout of the map is divided into four regions, the main central one with the biggest city as core, connected to three regions with high speed trains (currently TGV PSE, 270 km/h) or less fast trains (SBB CFF FFS Re6/6 with DEV inox cars, 150 km/h).
The central region has three main stations around its capital city. These stations are conected with an underground network for long, and more recently by suburban trains which go through the city between the western suburb and the eastern one or between the southern one and the eastern one. There are also some regional lines which still have one of these big stations as terminus.
Decades ago, very nice steam trains travelled from the central region to the south-western one. Now, double units of TGV do this job. The main city of the south-western region got a metro too, three regional lines serve this region. There are more cities southward which are about to be reached by the network.
The southern continent is connected to the central region by an undersea tunnel. There are two main cities and three stations which TGV stop at. Two regional lines run between the two main cities, a third one should appear imminently to serve the northern towns of this region.
Not much to say about the western region, the intercity from the central one stops at two stations before the bigger town which has a nice tram instead of the usual metros.
Anyway, Aristide, si les réseaux t'intéressent, il y a un sujet avec de beaux plans de réseaux dans la section française du forum