RBR were talking a while ago about producing their own engines. If RBR did go down that route, it would make perfect sense from both a technical and marketing perspective for a car manufacturer to get on board and for it to be a joint venture.
Who knows, AM and RBR might bring in Illmor or Cosworth in some capacity as well? That was being speculated here last summer:
https://thejudge13.com/2017/07/27/th...ir-own-engine/