I can only imagine how bad this is for morale. Out of the blue code review conducted by an external company means total lack of trust.
This was not a takeover by another company tho, which makes the Tesla participation super shady considering is a publicly trading company. Even if they're not participating in this as Tesla employees it would normally be a firing offense and compliance violation for a normal CEO to take people from one company to work on his other private company and allow the name to be publicized.