I got a thought, G, but I don't really know for sure if it will work. Hopefully, somebody will try to shoot it down here on the board and it is better to have that discussion than after you tried it and found problems.
Here goes--get some cheap epoxy resin. The Bondo Fiberglass resin that you get from an auto parts place should fill this bill nicely. This sets up pretty quickly, especially when it's hot so try to have all the rest of the "ingredients" ready when you mix the epoxy per Bondo's directions. Mix the epoxy and paint it on the steps with a cheap, wood handled, natural bristle brush that you get for around $.50 at the hardware store. When the epoxy has been painted on, toss on a layer of sand (steal this from the golf course sand trap if you have to--heh, heh, heh). If you don't want to make the golfers mad, get the sharpest sand that you can get from a builders supply. Don't mix up too much of the epoxy at once as, again, it sets quickly. You will need old tin cans or cardboard containers for the mixing and you will probably go through a lot of the cheap paint brushes--I would get 10. If you have a lot of seepage out of the cracks in the ties, you can put some modeling putty in them to make a tinker's dam.
OK, lets see how that plays. You might start by trying a small spot on one step just to see how it sticks. My guess is that with 15 year old ties, most of the surface creosote will be gone and the surface cracks will tend to hold the epoxy on the wood pretty well.