IMO, depends on the model. If built right out of the box, plain jane, put it where it fits.
If the builder took the time and effort to detail and weather it, put it where it would be seen.
Why not ask the owner where HE would like it.
Any issues placing the Walthers Cement plant (# 933-3098) on the other side of some hills where I have the Walthers Elevator (#933-3022)? I think the hills (about 6" high) that separate the two large structures indicate a break between different scenes.
If it's an issue, here are two other ideas: 1. put the elevator elsewhere and place the walthers bakery there; 2. redo nine feet of track and cork to move the cement plant in a different spot.
Thoughts? I prefer not to rip up the cork and redo track. I avoid that with the other options.