It is hardcoded. A neutrals ships cannot warp under any circumstances that I have been able to divine. I have heard reports, and even seen myself once or twice playing against neutrals of a neutral ship venturing through a warp point. But playing as a neutral player in several test games I have been completly unable to duplicate it.
It makes it quite interesting actually. If you happen to trade for or subvert a colony ship that is in a dead system, or any kind of ship anywhere pretty much, you won't be able to do much with it save patrol that system and maybe make contact with new races to have relations with.
Planets are definetly the thing to trade if you are a neutral empire. That's the only way to expand the reach of your empire.
I could imagine a decent strategy would be to build up your homesystem, trade planets with the first AI that happens by, and then capture all the planets in that system with troops. Then recapture your orignal planet in your homesystem and wait for the next AI race to happen by. Or figure a way to get the original AI to trust you enough to do it to him again.
Geoschmo
[ October 31, 2002, 21:12: Message edited by: geoschmo ]