I found this in the case book.
*8.3.3 SITUATION A:
During a try, a fumble by A1 is nearly at rest on the 3-yard line when a muff by B1 is judged to be a new force causing the ball to go into B's end zone where B2 recovers and:
(a) downs the ball in the end zone; or
(b) advances to his 10-yard line.
RULING: The try ends and the ball becomes dead when B2 recovers. In any ordinary down, such a dead ball in the end zone would be a safety, therefore, one point is scored for A in both (a) and (b). (4-2-2i; 8-1; 8-5-2b)
*8.3.3 SITUATION B:
During a non-kick try, A1 fumbles the ball, and in scrambling to recover the ball and avoid defenders, retreats into his own end zone where he is tackled.
RULING: This is a one-point safety where B is credited with a point, and A must then free-kick as normal. This is the only means of B scoring points on a try.
Apparently, B gets a point if ball is dead in A's EZ.