Well, real soul transmigration occurs at or before birth - most cultures that believe in transmigration of souls or reincarnation believe is occurs about the time a fetus becomes viable.
The soul in question actually chooses what family and situation it will be born into. There is no soul being displaced. In the case of Lois and Clark being sent back to previous bodies - Souls are outside of time and space as we know it. Their current consciousness simply awakened inside the other bodies - the other consciousness would either not remember the incident or think it was a dream.
As for Bill Jones... well, Clark had been shown to be an invenerate do-gooder all through his most recent incarnations. I doubt that will change.
