The European network is far more fragmented than it seems. There are differences in power supply, track width, station and tunnel width and signalling such that you cannot easily cross borders in a train. There are lots of trains that are equipped for multiple signalling standards and have variable axles. But in general, you can only go to the immediate neigbouring countries, as soon as you cross another border you have to change trains. In some countries, like France, you even have concurring standards within the same network. A hypothetical Lisbon-Moscow connection would need to change trains at least 2, maybe 3 times.
I don't think, therefore, that "total track length" has any useful meaning in Europe.
Here is some maps to illustrate my point:
https://commons.wikimedia.org/wiki/File:Europe_rail_electrif...
https://en.wikipedia.org/wiki/Track_gauge_in_Europe#/media/F...