Provided that not too much creosote was splashed onto the ground and that it is no longer running off, then they should be OK. Make sure that the trees don't brush against the fence until it is completely dry.
I understood that 'creosote' was taken off the market many years ago but last year I bought something called 'Creocoat'. I would have said that it was just the same thing!!!

it does the same job but minus the carcinogenic compounds of the tar based creosote. even smells similar. the new stuff is not meant to damage foliage either. so the plants should be ok.