NFHS only prescribes the bump and run when the throwin will be in the new backcourt. Otherwise, you administer throw-ins on your line.
No, Snaqs, it is not only in effect on turn overs, it is a bump and run anytime there is a throwin that goes to the backcourt sideline opposite the trail...perhaps in a pressing situation where the ball is knocked OOB by the defense on the lead's line.
Here is the NFHS mechanic from the book
NFHS Manual #128
c. Backcourt. The new trail official shall adminster all throw-ins in the backcourt and may need to change sides of the court ("bump and run") depending on the throw-in spot. If a quick violation or out-of-bounds situation occurs in a team's backcourt and reverses the direction of play so that the throw-in team is in its frontcourt, the ball will be in-bounded by the official responsible for that boundary line as in a frontcourt throw-in above (b).