The Technocracy used knowledge from at least one STC template to develop their civilization. The Technocracy military unit called "The Brotherhood" utilized power armor similar to that employed by the Adeptus Astartes.
The Fabricator Consul and his honour guard met with Warmaster Horus on the Vengeful Spirit after contact was made. The Consul mentioned to the Warmaster that his government had an STC in its possession; Horus drew his pistol, killed the Consul on the spot, and ordered the Sons of Horus to exterminate the Consul's Brotherhood guards.
Official records at the time stated that the Fabricator Consul's staff contained a weapon which would have assassinated the Warmaster, prompting the war against the Technocracy.