From a GA point of view, Alexa would appear to have got the answers to the question posed by the thread originator, and I like the idea the BS = Basic Service; I always thought it meant something else...
My question is this: with the new terminology, are we going to hear less of the stupid waste of breath statements like 'terrain clearance is your own responsibility' and 'land (at your discretion)'? What complete tosh. As aircraft commander, I know that I am always responsible for not flying into the ground and wasn't it always my discretion as to whether or not I go ahead and land after being given a clearance?? Surely, it's part of that old-fashioned pilot skill we used to call 'Airmanship'.
I fly offshore helicopters too. We have to ask the Helideck Landing Officer if 'the deck is available' (for landing, obviously). In the old days we used to ask for 'deck clearance'. No doubt (due to some 'duty of care' BS-er) it was decided that the 'deck is available for landing at your discretion' is a more appropriate approval than the more succinct 'clear for landing'. Believe me, on a foul weather day with a lot of traffic about, the last thing anyone wants is the frequency tied up with unnecessary bo**ocks such as this! I now sometimes say ' c/sign HLO, request deckability'. It seems to work too!
Sorry; rant over.
WW