Ideologically, why would a union own shares in a company? Not to mention the conflict of interest at pay review time.
I believe RHSL and RHL are wholly-owned by MAG, who these days are mostly owned by the banks anyway, since they mortgaged the shop to buy EMA and BOH at market value (based on profit multiplier and mortgaged on EMA and BOH) plus hefty premium (to block any other bids, mortgaged on MAN, which until then was debt-free).