Looks like two Porsche employees and two customers have admitted to a conspiracy to steal these engines. Their motive appears to have been financial. The thieves had been caught red-handed while delivering the stolen parts to a mechanic near Boeblingen. The parts had been reported stolen in late April.
That mechanic is well known for buying high-performance parts and installing them in vehicles for customers. In this case, however, they ended up at TechArt, who claim to have received them in error in response to a legitimate order. They also claim they returned all of them to the mechanic once they discovered their order had not been fulfilled correctly. The engines were never assembled at Techart nor fitted into any vehicle there.
However, the article does not state how much time passed between this discovery and the when the parts were eventually returned. Nor does it state if Techart made any attempt to document them in any way for e.g. illegal copies or reverse engineering purposes.
The local DA currently considers the case an instance of conspiracy, theft and dealing in stolen goods but not one of industrial espionage.