According to Amazon this is supported. Looks like its done by doing a put where the source is a also in s3, if you copy within locations there is no charge which is ideal (well it costs two reqeusts, copy and delete original but way better that download and re-put it). This tool doesn't support that option though. I'm no Ruby developer otherwise I'd have a go. I assume this is a new-ish feature as none of the perl libraries I've been looking at support this either. The article I was reading is;
http://docs.amazonwebservices.com/AmazonS3/2006-03-01/API/index.html?SOAPCopyObject.html