If the lot gets full, they will go through the lot looking for expired time limits on temp permits. Then they start towing. That's only if it gets full. If the lot does not fill up, they do not go around looking to tow.
When you get to the gate and do not have a GF, Contemp or Poly permit, they give you a date and time stamped permit with instructions to put that on your dash.
I wish they did it at BW too.
Don, DVC/VWL 2000
OS/90, BC/95, WL/97, Contemp/98&99, Poly/99, DxL/00, CBR/00