  This paper is the third in a series investigating the possibility that if we
reside in an inflationary "bubble universe", we might observe the effects of
collisions with other such bubbles. Here, we study the interior structure of a
bubble collision spacetime, focusing on the issue of where observers can
reside. Numerical simulations indicate that if the inter-bubble domain wall
accelerates away, infinite spacelike surfaces of homogeneity develop to the
future of the collision; this strongly suggests that observers can have
collisions to their past, and previous results then imply that this is very
likely. However, for observers at nearly all locations, the restoration of
homogeneity relegates any observable effects to a vanishingly small region on
the sky. We find that bubble collisions may also play an important role in
defining measures in inflation: a potentially infinite relative volume factor
arises between two bubble types depending on the sign of the acceleration of
the domain wall between them; this may in turn correlate with observables such
as the scale or type of inflation.
