Fireworks 8
Viewing post in NEXXT 3.0.1 released - bugfixes comments
Thanks! It seems that while most graphics editors settle for PNG-8 for indexed formats regardless palette count, at least Fireworks will optimize for the unusual PNG-1 format. It's plausible some other editors i don't know of do that too.
I've added handling for importing 1-bit PNG images, it's going to be in the next release.