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.