The french tgv system overheads look a bit different but I am sure they are functionally identical. Also TGVs have differently constructed tracks and no level crossings. The tracks are fenced off to prevent people and animals from getting in the way of the trains... I can see these things being problems for implementation... every farmer in the country insisting on getting his cattle or tractor to the other side of the tracks at government expense
They also dont share track with other ( slower) trains. This I can see might be a problem in some places having to add double tracks across the mountains for instance.