Using helvetica latex fonts...

Both of these figures look the same on screen, but

    > type1cm is used in the epsfile. Does backend_agg read the
    > rcParams dict during module import only? That might
    > explain this behavior...

No, it reads it in the function draw_tex. With the changes you made
in backend_agg it should work. Did you flush your cache after making
these changes and reinstalling.
When in doubt, insert some print statements in draw_tex to make sure
what you think should be happening is happening.

Confused in Chicago,