Some quick notes:

• Outside old city centers the buildings made after beginning of 60s have so thin walls that they provide essentially no cover
• There are aerosol weapons which shoot a gas-filled projectile into a room. The projectile then fills the room with an explosive gas
  Chechens have learned to combat this by moving their positions inwards in the buildings and lighting a bonfire in the room next to the window. This makes the aerosol gas burn safely before reaching explosive stage
• Upper floors of buildings are not a good place for defensive positions as they are easily collapsed. Fire spreads very quickly upwards
• Safest place for supply and deployment routes is underground using cellars, sewage pipes etc.

Updated 14:40: Here are some photos moblogged live from my phone camera. Quality is abysmal, as always