Civic Hybrid -- gas/electric usage

Does software control the switching of the power source between
gasoline and the battery pack? Or is it more of a mechanical element
that controls it?

Is it possible for Honda mechanics to "adjust" how much battery power
is getting used? I'm happy with my 2005 Hybrid, but I'd like to
average more than the 43.5 mpg that I'm currently getting. My driving
is 90% city (start and stop traffic). I watch the gauges closely, and
it seems that the battery doesn't get used as much as it could during
acceleration. In fact, very rarely does my overall battery power ever
dip below the 80% mark. I was wondering if they could adjust the
threshold/configuration of when the battery kicks in so that it gets
used more.