I had a paid F-to-J connection tonight. The checker at the bottom of the escalator scanned my BP and tried to direct me to AM. I politely said that I would check in upstairs.
At the check in desk, the agent scanned my outbound J BP (I also gave her my inbound F BP). She didn't say anything and then typed several things into her terminal. After a long minute, she reached for the BP stamp and I knew that I was in.