You can 'spawn' infantry. Sort of. Use the deployed Slave Miner for reference. Not sure if this works for vehicles and I'm not sure how 'Enslaves=yes' works either. Try fiddling with that.
Enslaves= can only be used once and its hardcoded to be SLAV, also its routine its hardcoded to be Harvest. All you can do is spawn a slave by that method. Ive tried it before.