NOTE, this is my first time playing/seeing this map.
Well I thought the map was decent. I do not like CTFs where you have to return the intel to the enemy base but beyond that I was not frustrated with anything. Overall I would play it again.
I noticed some nodraw issues here and there, but I am sure you already know about these.
I am thinking you should remove the block on the cap point. To me it is hard enough to get into the heart of the enemy base.
I know you are not really working on lighting yet, but to me I think the white lights are a bit too bright or too many inside the base. The spawn room and intel room has way too many lights, I think you only need two rows of lights.
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There are some optimization issues. In the wireframe screenshot I can see decently into their base. With the current layout the only way to stop this is open/close areaportals. You could make the spawn room exit doors open/close areaportals but then these doors can not have windows. The spawn room with the big window would then need to have their own doors with open/close areaportals so a player can still see through the big window. This would be helpful since one side of the enemy base is closed off from viewing. Other then that I can not figure out how else to help this situation unless you make the hallways longer/narrower and more 90 degree turns.
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The spawn room "emergency exit" that exits to the ledge overlooking the courtyard: I think the door should be at the end of the hallway instead. With the current door I can not see out onto the ledge for any sniper lasers or other enemy. I am thinking a similar spawn exit to 2fort for the ledge.
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I got stuck repeatedly by running along the trains and falling down between them. A clip just needs to be added. This happened on all boxcars.
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For the middle not sure what you should do. I heard complaints about snipers. I was never hit by a sniper so I dont know. If cover is really an issue I would scrap that whole mid structure you got now and make a enclosing structure similar to the brick detail building with the three tunnels off on the sides....or a structure like cp_well. I know detail is not an issue yet but to me the current structure in the middle makes me wonder what is it's use within the environment? A catwalk over the train track? I also wonder if the one exit coming from the lower level of the middle, going towards the dump trucks, is a bottleneck? I do not see any way for most classes to get up to the second level if they are in the lower level between the trains. Is it worth while to move one of the boxcars down the track so the stairs are accessible from the lower level middle? But have the moved boxcars be opposite on each side, so like for red side the boxcar near the missile on the ledge is moved down while for blue the boxcar not near the missile is moved down.
In terms of sentry spots, I put up a decent one in a random spot within my intel room. It lasted a few minuets and stopped two or three caps. As of right now I do not see any overpowered defensive sentry spots. As for offensive I would not even bother since it is a very open map.
I agree with Remnic and stevethepocket, the spytech theme in recent screenshots fit better.