I have actually been to Toyota City in Japan. They use mostly Mitsubishi but Toyota is not really interested in buying individual controllers. They buy the whole machine. While it is preferred Mitsubishi is on the machine it is the machine that is most important.
I was there trying to sell Toyota motion controllers. Toyota has RMCs in battery testing machines but they were integrated by a division of Parker Fluid Power. Toyota didn't seem to be interested in integrating themselves. BTW, we are a Mitsubishi alliance partner.