I don't know of any redi mix facilities that would get the powder from a railcar, it's usually trucked in, from a storage facility, or even a transloading facility, where the truck could load right off the rail car, than deliver to the redi mix plant.
You could make your redi mix company part of a big cement supply facility that would receive it by rail.
I think Walthers had a kit for that, too.
The old plant I worked was just a stand alone batch plant, as I described earlier.
The newer plants have the operators area in a building that can be attached to the plant, or seperate. The one I'm most familiar with, the operators office is on the second floor of a garage/repair building, that is right next to the plant. He has a good view of the plant, and the truck as it enters, along with monitor screens he can view, of the area. All the gates and valves are controlled by electric relays, and not the levers, like the old plants.
Portable type plants, like what road builders use, the operator is in an office trailer, close to the plant.
Just about any type of building you can come up with could be the plant operators office. It doesn't have to be a tower.
As far as the aggregate part of it all, it's common now for the conveyor to be covered, and come from a covered loading area, where the front end loader fills the different hoppers, especially up here in the northern states.
For winter operations, the bins up in the plant have steam lines, so the aggregate can get heated, and hot water is used for mixing.
If you search for concrete batch plants, you'll get lots of images, big and small. I don't have any pictures that I have taken personally.
Mike.