On Wed, 21 Dec 2011 18:09:55 +0000, The Natural Philosopher
wrote:

Is it possible in a pinch that the driver could pull down his
pantograph, drive round the stricken trolley-bus, and connect up again?

Not without a battery or auxiliary power of some other sort, no..

Glasgow trolley buses had just that. They moved under their own power,
albeit slowly, so could in fact overtake a broken down one, or
relocate to the other side of the road.
The low speed indicated to me the battery pack wasn't very large.