Having operated 11&14 both ways on the highline, twice (on one trip dying on the law in the siding at Almanor, where we met #14 in broad daylight), I can say this: the presence or lack of signals isn't an issue (the CTC ended at the West end of Robber's Creek at the time). What are issues is that it takes too long to go this way and that the BNSF has said "no, because we run too many freight trains over the line; there are simply no slots for passenger trains".