i cant see why not as long as they are dry. a few years ago i sanded down some reclaimed hardwood ones which had been used on a railway and treated with creosote and or bitumen. i used an angle grinder with a sanding disc to clean them up for used in the garden i wasnt after a super smooth finish. the dust irritated my skin making me come up in a red itchy rash (just wearing shorts and boots was a big mistake)
Some one brought what looked like softwood sleepers. And asked me to if I could cut to size and give them a decent finish. They were tanalised so I planed the top layer off and cut to size. They came up pretty well but there was a lot of checking from drying out. He wanted them rustic and was planning on staining them.
Thanks for replies. Ye I'm wanting the rustic look too. So a bit of checking is fine with me. Will let them dry out for a good while before I do anything with them.