my neighbor just took his evo to an LA county signoff place and they sent him back home because his zip ties were not "permanently affixed to the vehicle". I think it depends if you get a jerk or not. The fool proof way to fake them out is to cut the tops off of the screws, tape them to the license holes and then 3m tape the plate to your bumper. so it looks drilled in.
oooooor just hope for someone who isnt a jerk about everything.
edit: oh and bgr's idea about using the holder to make it look natural sounds good too