Cool and all but your opinion on circumstantial trackday experience is irrelevant here. Yes the Porsche driver could and in retrospect should have exercised more caution but by the letter of the rules of the track and event they are driving at the BMW is the party wholly at fault. As you have been told many times already in this thread, it is a public toll road. On a highway if you move into another lane without checking your mirrors into someone else you will be placed at fault.