You will find the Carril Rąpid lane - yellow signs - on the left side of the security check entrances. But as you indicate the passport check, slight further on, left hand turn, is where it can get sticky. I had a flight a few weeks ago when the problems were getting into the press and BA were asking passengers to arrive early, but as it happens it wasn't too bad, under 5 minutes certainly. The underlying reason for the delay is still there, the need to scan all passports when the Spanish computer system wasn't really designed for this, and is also evident in other parts of Europe too (AMS, Italy) since they were part of the same tightening process. BCN is usually one of my "turn up one hour before departure" airports, and I suppose it's now in the 75 minute brigade, but still, I hope it won't be so bad.

My guess would be that the pressure time is when the other non Schengen longhaul departures to Ireland, UK and longhaul are at there greatest. Certainly an evening flight should be OK.