Self Driving Cars - Just what can they do?

[David's8]

Self driving vehicles are getting a lot of newstime right now but, just what can they do and how do/will they react in differing circumstances?

Can they overtake another car ahead of them? e.g. can they, on a clear open road, when coming up behind a tractor overtake it or do they just form an orderly queue behind it? What happens on more busy roads where overtaking is a more complex task requiring assessment of lots of issues - oncoming traffic, vehicles joining from side roads?
What about when you (driving a driver operated car) wish to overtake a queue of self driving cars. Will they allow you in in the middle of the queue and how will the SD cars KNOW at which point you need to get in to avoid the traffic coming in the opposite direction? I know that vehicles should keep a suitable distance apart to allow a car to move in but many don't now and I understand that SD cars - like the trucks currently under test - may well keep closer to the cars in front. (At least you may not get the irate gestures for undertaking a perfectly safe manoeuvre only made hazardous by some drivers annoyance at being overtaken!)

If they require a driver's assistance in dealing with issues such as the two above, then they are not really driverless.
What are other's thoughts?