It will be really tricky to tackle the intermediate scenario where both Self-driving and human driven cars exist on the road. One possibility is where until the technology gets sophisticated, regulations might require a driver to ready to takeover in case of danger at all times. After this phase, self driving cars might be able to handle different situations better like a good driver. However, there still might be different scenarios but the technology should be able to take quicker decisions or better yet avoid getting into such situation.
It is an interesting scenarios that you have described with the ethical decisions. There might be no straightforward way to tackle the murky areas but government might regulate even the decisions or a body similar to CAA will set standards based on which car imports might be regulated. I don’t think leaving companies to self-regulate which is a potential recipe for disaster as we have seen before in financial sector.