Of course I am not suggesting you do this, but there is a way in fact.

Check in at T-2 as usual for the IB flight.

Buy a one-way completely refundable J ticket to somewhere from T-1, and do OLCI and PYOBP.

After checking in at T-2, walk through to T-1 landside, and sail through Zone R security with your BA PYOBP, and on into the lounge.

From the comfort of the lounge, call BA and say you missed the flight, could they offload you, and refund the ticket.

The go and board your IB flight.

It would of course be a shocking abuse of the system to do this, which is why I would never ever dream of doing this.