Are you only interested in running the car with the pack physically removed?
My understanding is that it can be done if the junction board is left in place, connected to the other IMA components as it normally would be.
I ran my car from July through November, 2011 with the pack/IMA disabled, but still in the car: the big breaker (ON/OFF switch on the junction board) was in the OFF position. Best to do this if you're having pack problems anyway, to avoid doing further damage to the cells.
The car reverts to using its conventional 12v starter, and obviously all hybrid functions cease (assist/regen/autostop). The DC-DC converter still worked fine, and kept the 12v battery charged (with one irregularity: sometimes there was a delay before the DC-DC came "on" for a moment after starting).
This thread on insight central seems to confirm this, and comes from the horse's mouth (Ron, of hybrid battery repair):
Drive without the IMA/Battery? - Insight Central: Honda Insight Forum