Thanks for the kind words, guys
re Kaliyuga: It slows down cars (if they only drive slow into it it will stop them), tanks just smash throu ;D
re Skaven: Thats the tricky part I'm trying to figure out at the moment.
Opening and closing is possible if you stand near the gate, you'll have a new entry in the action menu. You can also order Soldiers under your command to do it (if they are near the gate).
How AI handles it is rather bizarre.
Foot-Soldiers walk around it wich is what I expect them to do. Vehicles just drive throu it, if you set them to combat mode they drive around it. I tested it with other fence-like objects and found that vehicles don't seem to notice if you place a barriere on the road, they crash.
What I have in mind is some kind of script that lets the vehicle wait in front of the gate if it is closed, if it's open they should go on. I'm studying the command reference for some kind of command thet lets you test for different states of animated objects and let you open and close it with script commands. Haven't found it yet.
If someone knows how to do this, cantact me please
EDIT:
I have found the commands