Are Shimano R440 road flat bar shifters compatible with a mountain bike front derailleur? The Shimano shifter flat bar series have the same cable pull length than the mountain bike shifters.

Is this series compatible with a mountain bike front derailleur, Deore, for example?
There's a great thread here that describes some of this. Here's the meat of it though:


  Shimano's assertion that you need to use "flat-bar" front derailleurs
  with "flat-bar" shifters is false.
  
  When working with Shimano, "flat-bar" shifters are really just
  mountain-bike shifters in different colors. This doesn't make a
  difference for the rear derailleur (Shimano has standardized the cable
  pull across all of their shifters), but there's two different cable
  pulls for the front derailleurs. "Road" front derailleurs require less
  cable movement than "mountain" front derailleurs for the same amount
  of lateral cage movement.
  
  This has a couple consequences: 
  
  1: operating a "mountain" front
  derailleur with a "road" shifter will result in insufficient cage
  movement to make the shift. This is rare in the recumbent world.
  
  2: operating a "road" front derailleur with a "mountain" shifter will
  result in the shifter jamming before the internal ratchet catches,
  meaning the chain will shift but immediately return to its starting
  position. In other words, the shift fails. If the shift succeeds,
  often the shifter will jam at that spot and not allow the shift in the
  other direction. This is very common in the recumbent world.
  
  
  the longer pull of the "flat-bar" or "mountain" front derailleurs makes for lighter pull at the shifter when using SRAM twist-grip
  shifters. This can be an advantage for people with slippery hands
  and/or weaker hands.
  
  
  "Flat-bar" front derailleurs also have cages that better match the
  larger diameter chainrings typically installed on road bikes.
  "Mountain" chainrings are typically smaller, and trying to get a
  "mountain" front derailleur to work on larger chainrings often
  involves compromised adjustment or hand-modified cages.
  
  My favorite "flat-bar" front derailleur is the Shimano FD-R443. (This
  is roughly Sora/Tiagra level parts: cheap, durable, and relatively
  attractive.) It's since been superceded by the FD-R453, which has a
  taller inner plate to match newer Shimano cranksets, but I like the
  FD-R443 for its greater adaptability to different chainring
  combinations.
  
  I've been using the FD-R443 on several bikes, operated by Shimano
  Deore LX and XTR and SRAM Half-Pipe Attack shifters. It's always
  worked flawlessly.


So no, not really. You might be able to find a combination of gearing, derailleur, and cable pull that will work, but you're probably still better off finding a matching set.