My last try:
Perhaps someone will recall if there were any such precautionary trackwork measures on bridges on the original Waverley route; a cursory look at old photographs and films of likely places has failed to find any. Trap points abound and check rails can be seen on curves but I have not so far been able to find evidence of any guard rails on this part of the Waverley route.
This is, for me at least, an interesting contrast of safety standards between then and now. For some, used to the older standards, the new arrangements might appear 'over engineered' - not that I am suggesting they actually are.