We received the marhaba service last week, we are currently only blue and were on a reward 241 in F.
We normally pay for it but had decided to stop at the meridian for one night due to the late arrival time so didn't bother, we were then a bit shocked when they were waiting for us at the end of the airbridge and until reading this we have been trying to work out why we had received it.
It can't have been the hotel as it was just a cheap room only booking through booking.com
F was only half full so maybe they do offer it to a set number of passengers not just those with status?