A somewhat related case in
KLAX 2006
In both cases the engines were running for purposes of ground test, not for flight. Ergo, the definition of "aircraft accident" was not strictly met.
In the LAX case, the NTSB immediately became involved because of obvious safety-of-flight implications, even though the US OSHA would ordinarily cover it.
In TLS - who knows? Would the French equivalent of OSHA have primary responsibility?