Once the pass is touched by B, EVERYONE is eligible to catch the pass. We had a lineman catch a batted pass and score a TD this year. Makes for interesting stats when #73 has one catch for a TD.
Couple of years ago, I also saw a correct call made when the passer threw a pass like this, it was deflected back to him, and he threw another pass. It took the R a few seconds to realize it, but he dropped the flag for IFP. Can't throw two forward passes on one play, even if the first one didn't cross the LOS.