The concourses are now called A, B and C. A is new and EK only, B is what used be 'Concourse 2' and EK only and C is what used be 'Concourse 1'.

The people mover goes between A and B. B and C are linked airside so you can walk between them.

The people mover has two tracks, at present one is used for 'dirty' passengers arriving at A to go to Immigration at B. The other track is used for 'clean' passengers and runs from after the passenger search area at B/T3 to the departures area of A, carrying passengers in both directions.

Buses will most likely go to B only. Some A380 flights are still departing from B. Likewise, some 777 flights arrive and depart A. If you wish to visit A, you can go there and return on the 'clean' train, so quite an easy process.

I can only assume there is transfer security available in A.