Continuity mistake: 12/4/13: When Sharon claps her hands to get everyone's attention to tell them that her and Jack are not getting married, look at Kirsty - she is looking at Sharon over her right shoulder, but when the angle changes Kirsty is facing forward, and then turns her head to look at Sharon over her right shoulder again.
Other mistake: Friday 12/8/11 Greg leaves for his holiday in Mexico by taxi. After he has gone you can see his pick-up truck parked in front of Dot's car in the square. On Monday 15/8/11, Greg's truck has gone.
Answer: Albert Square is a set in the BBC studios in Borehamwood, on the north side of London. The trains, to the best of my knowledge, are simply a bit of the old TV magic. As far as the extras go - it's not difficult to get extras in reasonable numbers through agencies.
Tailkinker ★