I already made an observation y'day - the entire MAS- CSTM route is the most neglected. Having traveled along that route 100s of times, I can say it has only deteriorated in terms of upkeep (very filthy) and speed. Trying to introduce any kind of high speed train on those neglected lines is a recipe for disaster.
Entire stretch is politically very volatile and prone to tampering by miscreants. Even MAS- CSTM mail (or the reverse) derailed once on its route..slowest train..