It will be a quite tricky process, if not quite impossible. Removing creosote from railroad ties can be done, but the risks and the work of doing it might be greater than the results.
How to remove creosote from railroad ties?
An old, used creosote treated railroad tie will be deeply penetrated by the toxic substance, one method to try would be the sandblasting but the depth of the creosote penetration in the wood is the determinant.
Also by sandblasting it you expose yourself to the fine sawdust which is contaminated with the well known toxic creosote substance which is known to be carcinogen.
Another way of removing the creosote from the railroad ties would be by sealing the wood. Now I know that is not truly removing the creosote but sealing it might help lowering the chances of the substance getting into the soil.
Is there an easier way of how to remove creosote from the railroad ties?
The third option would be available if you are in the possession of a bandsaw. You can cut out of the all 6 faces of the railroad tie up to a couple inches, or as much as is needed to remove the creosote impregnated wood. By doing so you will end up with a thinner, smaller railroad tie.
All of the options mentioned above don't guarantee the successful removal of the creosote, the substance might have gotten really deep into the tie, making it impossible to remove.