I can report that the system does in fact work. The agent manning the barrier was slightly surprised when I announced I had a smartway booking and needed to fish out his phone to scan the QR code. After verification I was simply led to the front of the normal priority line (at the preparation tables). So this will save time in virtually every case, if one can predict the arrival time within the allowed plus/minus 10 minutes timeslot.

I hope if this becomes more popular they will actually introduce a fully separate lane. If not then the already grumpy passengers at Europe's perhaps worst performing fast track might start a riot.