Ah, so it's essentially acts as Epsilon's "economy" gimmick in their tech tree.
Soviets have the Maintenance from Industrial plant. Allies have warp miners. Foehn has spinblades.
personally i think that the war rig is an ill fit for epsilon considering they already have mind control and grinder for extra credit (which is also getting buffed by having a mobile grinder)
i reckon that it would be a much better fit for the allies since they are much better at setting up mobile defenses and it would work very well with their other ore based late game abilities, which are quite lacking at the moment