One of the first things I noticed, was the HL2 textures in Blu spawn, you might want to take those out and replace them with some tf2 models (crates perhaps?) Also in the blu spawn the stairs had some nice brushwork but they seemed way to large, and the area they opened into didn't really seem that worth it to go. The doorways also felt a tad short.
On the outside, I saw the pipeline Idea and I liked that. However the extremely long payload track looks like its going to cause problems. The map in general looks way too big, like Chaopsychochick said. I personally felt that the sides where the cart goes are going to be completely unused. Also a few areas just seem bland. The giant silos, while cool, seem more a problem then a thing to help defence, it's just way too large to use effectively. Also it looks like Red would have problems defending since there is such little cover.
The warehouse was interesting, the concept is good, multifloor fighting but the way its setup now it just seems so bland. The hundreds of props most likely wont be great for optimization as well. Its basically looking like I would fight in Big Room #1, then 2 and so on.
I know this is beta but, the explosion was confusing, what did I blow up, what value did it have? There was also no indication to it, it just went boom on the tracks randomly.
*bugs*
-The alternate exits at blu spawn made opening sounds in setup when i got close to them
-Blu can open the red spawn doors at the train depot spawn in the first cap
-last red spawns have invisible doors
Overall, interesting concept, try to resize your map and try to generate more cover and heights for the teams.