ATPMBA---Usually the crew sits and the plane continues. Everybody HATES these 3/4-hour 'practice layovers' and would rather be flying. But, because of the direction of flights leaving the hub EB/WB, usually crews wait for a flight departing to the direction from which they came. Most major US carriers have'nt figured out this inefficient, unproductive waste of crewmembers.
They'd better.