I believe you have to set them up on a map in world builder and it acts like the tunnel network.
You can have multiple cave networks but the caves that belong together must have the same index number.
The reason I don't want to use tunnels is because we're already using those. And we don't want these new tunnels to connect to those of the other system. And another thing is that CaveContain, according to DeeZire's guide, allows you to specify which KindOfs to allow. That last part is essential to the logic we're trying to create.
I do believe there was some sort of Cave that was either in one of the missions or was discarded. If you look in the General/Zero Hour BIG files, theres a tga with a "cave" cameo.