As of this morning, my experience is it is NOT possible to do this.
I was 2nd in line at the gate to enter DCA at the non-early opening while my party was in DL. I was intended to be the fastpass runner and had all our physical tickets, which were originally E-tickets purchased and linked on the app, but they had only been scanned at DL so far. There were cast members walking the fastpass line saying repeatedly "You cannot pull a fast pass for any ticket that has not already been scanned into THIS PARK." (So I wasted an hour in the gate line, had to get out of line and meet my party to scan them into DCA and get back in fastpass line. Life of a runner.)