Digital BW, The Print

Forgive my asking what may be an obvious question to some.  I'm aware 
that the UT2 inks can make a good B&W print without using false-color 
curves.  But how does it work when you don't use curves?  How does 
the driver know in what proportion to mix the different inks to 
produce the various shades of gray?

Also, are prints produced using the curves better than ones produced 
without them, or is it about the same?

I plan to switch to UT2 once I get my 1280 cleaned and use up my last 
UT1 cartridge.

--Peter