"My garden has been lined with RR ties for the last 10 growing seasons and I have never had a problem with anything bad happening towards my crops with whatever's been applied to the ties. I think they make a great border for a garden."
There is a good chance that the railroad ties will out last you. Therefore you will not have to replace them. Your concern should be with the soil. If the creosote and whatever else is in those old RxR ties has leached into your soil in the last 10 years has now leached into your body from the vegetables you have consumed. The qoutes below are telling you something.
"As far as treating the logs go, I wouldn't use much more than some kind of oil. Remember, whatever you treat the logs with will end up in your garden soil, and eventually, in you."
"real railroad ties were in ages past "preserved" with creosote.
creosote has some suspected health concerns."
Seems like good advice.