I doubt that it will be affected other than having overhead
cables and stanchions installed. The bridges which need a
re-build are, I assume, those which go over the railway and
currently do not provide adequate head room.

I wonder if, when the platforms are prepared for longer trains, the
entire platform will be re-furbished or only enough for 4-car trains.
Many of the platforms are long enough for 6-car trains. It might
be a short-sighted approach to cater only for 4-car trains.