Flipping channels, I came across a UFL game, and watched one down. On that down I just happened to watch, teammates of the ball carrier started pushing him from behind, trying to push him across the goal line. They ruled progress stopped at the B-1 (plus/minus). The announcers then reported that, in the UFL, when teammates begin to assist the BC like that, progress is stopped at that point, and the ball is dead.
Good rule, IMHO. Better than a foul. Just kill it.
NCAA needs this rule (and so does the NFL). That “tush push” thing is bush league.