Traintown is quite difficult to navigate ( particularly when looking for cps ) because of the general openness between Mid and Last, a lot of areas exist that are entirely cut off from objectives, if you want your players to actually cap points, this is bad design. In a competitive environment these disconnected areas also discourage pushing out of Last, as teams will have to check SEVERAL areas for back cappers before they can move forward.
I also noticed that the points themselves were placed quite randomly across the map, with Last flowing into Mid and Second sitting off to the side. Logically, people will go straight forward after capping Mid, having Second off to the side like this breaks the flow of the game quite a bit.
While these outside areas were excessively open, the indoor areas were excessively closed. Small doorways and low ceilings ( specifically above Mid ) make for slow gameplay. Consider the blast radius of a sticky bomb when designing indoor space and chokes, you always want to give players a means of avoiding damage.
I'd also recommend that you de-clutter your props, there are far too many crates and such that act as obstacles more than cover. You used a few large foliage props as well, in a competitive environment, people don't want to deal with stickies and sentries hidden inside props like these, so I'd personally save them for out-of-bounds areas if I were you.
Oh, and you mentioned that there was a train at Mid, the cover surrounding the cap makes this a non-issue, as you can't really be knocked down into the train's path. Mid's capture area was far too small by the way, and difficult to read without the usual hazard stripes.