I was working on the bais that if 256k is the highest bitrate they have available for download, then logically they can't stream at a higher rate unless upsampling. I guess there could be different licensing arrangements for downloading & streaming & so could be using different source files. Seems unlikely though.
I would have thought that if they're going up against a well established model at the same price, they would at least need to match the bit-rates already on offer.