All is dependent on airline. When in an EE seat on BA short haul, the scanner at the gate beeps 100% of the time. 98% of the time,when departing London, the agent will point out that its an EE seat, or ask if I know that it is one. When leaving outstations, I find that they only ask at the beep maybe half the time........if that. On the plane, they always do the talk, take a look at the pax and ask if one speaks English. I have seen them answer half nods, and I have also seen them insist on short conversations to see if the pax speaks English. This is the way it is supposed to be. As I mentioned above, I have on many times brought up issues and had people moved when the FA's are not doing their jobs properly.
Unlike some above, this is not a ridiculous policy to have, and as said by some above, the requirement on non-English speaking airlines the requirement is the language of the airline or English. I don't care if such exits have only been utilized twice in 20 years, I feel safer knowing that the people at those rows can understand instructions and at least seem physically capable of performing the unlikely task if need be. A 90 year old non speaker with a cane does not fit that description.