Don't think so. I haven't seen anything like that before. Usually if you want to fill the tanks from a hose you can screw on a hose tap fitting to the filler ports...
The normal setup is for that inlet to run (via john guest push fittings) to a pressure limiting/reducing valve under the floor about where you were kneeling to take the picture. Then from that valve to a tee piece in the black cold water line. My guess is you will find a joiner in the line right where the tee used to be.
So you will need a new female thread (3/4 possibly) to jg push fitting, a length of jg pipe, a prv with an integral check/non-return valve, a u clamp to secure under the floor, 2x male thread (again 3/4 possibly) jg to push fitting , and a jg tee piece.
Make sure the connections from the inlet to the valve are perfect as a leak there is at full pressure... Speaking from experience...