Sid
As far as I am aware at Heathrow the operation is land one runway and depart the other with the odd time as foghorn says that there are simultaneous arrivals. The ATIS info will in this case be the designated landing runway.
If there were arrivals on both runways all day long the delays to departure traffic would be too long. I believe the simulaneous arrivals are only to alleviate some of the backup in the TMA. The changes are minimalised because flow is a lot tighter (only one runway to land on) and when an aircraft is given a change there is a lot more time to do it...ie in the holds or on initial approach.
Toronto has 5 runways...and a peak operation is called a triple ..Land 2. depart one. Land 23-Spacing 5 miles. Depart 24R , Land 24L spacing 3 miles.
The ATIS will give the two landing runways but as I said before we can't always fit the aircraft in where they are initially told.
Unlike Heathrow, Toronto also has a straight in fix so you have aircraft coming in from all 4 directions they don't hold here like they do in the London TMA (they are sequenced to come in 10 miles apart). Peak rate is about 60 an hour in the triple operation and it can be tough to judge the balance on each particular runway. Then as I said in my previous post aircraft have to go where they fit.
I would prefer the Heathrow operation at times as it is easier to regulate but then again I am sure Heathrow would love extra runways....and then you would have the same problems that you experience elsewhere.