One of the main problems of electrifying any existing rail line has been the problem of track time and consequence expense. Any construction has taken many months and the example of how long the NEC from New Haven - Boston took is a prime example. There has been the same problem in the UK which Network rail has long been trying to do something.
Network has now ordered a "factory train " from a German company that has the capacity to construct 1.6 Km of CAT a day ( ~ 1 mile ). If ( and that is a big if ) this concept works out this may solve one big major problem in electricfying. The savings of unproductive infrastructure ( sunk costs ) in place but not being used can be significant…
If someone can get more information it would be appreciated