I found the bug in the exported BMFont xml file and think I should share as I believe it's not so easy to track down.
I included very small character subset (only digits and few letters) and there was no kerning between the characters inside the exported atlas. The generated xml was not valid and it had to be corrected manually. 2D Toolkit tried to parse it as BMFont text file and found no characters.
Instead of:
<kernings count="0" />
BMFont writes:
<kernings count="0">
Hope it might help someone.