All models are 100% easy to convert from 3ds. Download it, import into Nifskope, save as nif. Import into blender, export back to nif and its ready to go, the problem is, as you were saying, that the models are sort of very detailed, so the simple ones are much easier. Something like the chronosphere I can tell just by looking at it, when i convert it, the models going to be about 1mb big, and I never want a building above 100kb, usually 50kb.
Thats when the work comes in and you have to simplify it by removing details, but many of the things you posted look very detailed and it would be hard to convert to a decent size, lemme take a closer look at them and see if any will be nice in cIV
EDIT: Also I can only convert them if they are in .3ds, many of those models only come in obj
Also I already converted the transmission tower you listed. It is under new broadcast tower. Would you like the building to go along with that?