SpaceX uses some Tesla parts (such as electric motors and batteries). Apparently, SpaceX has used Tesla engineers as consultants regarding those parts. Legally

SpaceX uses some Tesla parts (such as electric motors and batteries). Apparently, SpaceX has used Tesla engineers as consultants regarding those parts. Legally, Tesla isn't allowed to do "favours" for Musk's other businesses. From what I understand, SpaceX/etc pay Tesla the fair market value of all assistance received (both goods and services). And the cooperation has to (at a high level) be approved by the respective boards (both Tesla's and SpaceX's) while Musk is not in the room. Whatever assistance Tesla may have given Musk regarding Twitter would be subject to the same legal requirements.