Whan I'm using a default Camera LOP the motionblur on my particle simulation is correct. When I swithc to an imported(ABC) camera there is zero motionblur. Camera is static. I'm after my velocity motion blur for my particles. The results are the same if I import the camera from SOP of directly the alembic in LOPS.
What I tried so far:
motion blur LOP
camera edit LOP
cache LOP
Nothing worked so far.

Is the shutter set correctly on the (alembic) camera? You said you tried the camera edit lop - did you set the shutter there (-0.25, 0.25 is default)