It just seems obvious to me. When all cars are self driving, and one or more self driving cars needs to negotiate an obstruction caused by parked cars, it will simply communicate the problem to the parked cars which will spring into life, all vehicles in unison then follow an optimised sequence of manoeuvres to allow passage, rather like a giant sliding block puzzle.
Other problems will be solved in a similar way. For example, driving down a narrow Devon lane that has become just too narrow owing to overgrown hedges. The car will simply solicit assistance from the nearest farm tractor with hedge cutter fitted, which will soon appear (driverless, of course), blades spinning, clear the obstruction, then retreat to its cosy barn. The farmer will never know it happened.