Just to clarify, last year we missed our DME bus back to the airport (long story), and the CM at the DME said there was no problem, we'd just catch the next bus, which was about 45 min later. However, we were told that they would not guarantee we'd make our flight (we made our flight with over an hour to spare).
But, I wouldn't bank on this. I'm guessing they'll try to help you get to the airport as soon as possible, but if the next bus is full, or the next bus isn't for 2 hours (unlikely), you could have a problem.