Placing multiple inductors (buck) close to each other on PCB
What will the inductor shielding effectiveness be? There is no
  specification on distance vs field.


You can do a simple test - use 100 kHz (from a signal generator) applied to one inductor and see how much induced voltage is in another inductor when placed close to the driven inductor. I wouldn't want more than (say) 2% coupling (2% voltage induction). Rotate orientation to find least coupling and then design your PCB.