I'd say it would crash. Police would know what's on that tile and should avoid this scenario.
Not always possible: I had a single tile to place, on the empty spot my helicopter was on, and I pulled a tunnel tile (and didn't have Traffic Camera in play). Fortunately, the driver didn't go that way, so I didn't have to resolve the dilemma that time!
But I was thinking either instant destruction, or pay an enforcement token to move off the tile.