Velocity is relative. There is no special reference frame that would be "at rest".
But acceleration is not and was never claimed to be. Reference frames in free fall are special and reference frames that are accelerating relative to the ones in free fall contain inertial forces (circular motion involves acceleration towards the centre; the corresponding inertial force is called centrifugal force).
So you can distinguish which of the stations is rotating and theory of relativity never claimed otherwise.