It's not optimized for use with godot since RPGM's autotiles work quite different.
Only some of the floor tiles are autotiles though and you could basically use those on a 24px grid instead of a 48px one. Since an autotiles is basically 24x24px corners, 48x24 / 24x48 long borders and a 48x48 middle.
The rest is normal 48x48 tiles.
So it is possible, but not optimized for godot's autotiling etc.