The designers describe the app: "Have fun riding the subway while finding and checking off all of the characters that subway commuters know and love. When you get five in a row, BINGO!
Created by New Yorkers, this game features beautiful artwork and an insider's attention to detail. Subway BINGO is a totally fun way to pass the time on the train or subway platform....Dozens and dozens of real-life characters, moving subway doors, and more!
It would need to be Tubecized / anglicized to cover London but I reckon it would be popular.
In fact it reminded me of the spoof video of teenagers playing "Tube Poker" - supposedly "an illegal gambling craze played on the London Underground".