It will possibly be near impossible to in the short term remove all traces of the spillage. However, there are ways to reduce the discolouration. What I would do (assuming there is no immediate risk to adjacent vegetation) is to in succession liberally wet limited areas with white spirit, rub/scrub and then wash off, perhaps after additionally applying some detergent - note that the washing mudst take place before the white spirit has evaporated. I would hope the creosote/creosote-like substance will mostly be removed, but any remaining traces which have soaked into the surface will then gradually weather down over months and more.