Project Tomahawk:Storm is just a rather old fashioned mod for VGen adding new units, upgrades and special powers while enhancing the current arsenals of all factions. 110% fun guaranteed. tl;dr it's Backwards Compatibility: The Mod.
This is a new feature/addition for the next version already somewhat spoiled in previous media. Each mission grants you unique units in place of their normal counterparts.
The unit list is given via a message box like the one in the training mission after the intro scene of each respective mission.
The things you see listed for every faction are more or less final for the next release, although I'm seeing if I can work to do this for more units in future versions.