We don't allow drivers to present themselves at the border without an entry number, sometimes driver's being human will cross in the spur of the moment and those times are dealt with accordingly. AMPS fees suck (they were taking it easy on them until recently), so we are extra diligent to ensure no one crosses until their shipments are accepted. What we won't do is wait several hours on our time after a driver has arrived at the bridge and is still not cleared when we have done everything on our end, following proper procedure. In those cases, we bond the load as it is cheaper to bond than to pay a driver to sit for an unknown time, and fail on the driver's next shipment sitting in our yard that the driver is to turn with.
To answer the bonding question regarding inbound from US to Canada - it is very easy now. No more A8A, just adjust the e-manifest, resubmit and now the load is in bond. In regards to LTL, it is only the bonded LTL that sits in bond, everything else is cleared.
