I can't help but love it when things like this happen to the extremely affluent. Seriously they haven't paid their tax bill for 30+ years. I personally hate the fact that many HOA can auction off your house if you don't pay you dues, I've heard of soldiers serving abroad finding out that their house has been auctioned off because they owed $1k, and the person that bought their house for $20k has already flipped it for $100k, but this is a case in which the city waited 30 years to try to collect.
The homeowners are arguing that the city should have given them notice. I'm guessing they did, they simply sent the notice to the address given to them. For a $1000 total bill I highly doubt the city has time to canvass the neighborhood with signs and since it is a private road, I'm guessing that the security guards might even the city officials a hard time getting in.
I would love it if the people that now own the street both charge for parking and open it up for bus tours. I would feel a little bad for the home owners if there were a bus tour as they likely paid a premium to live on a private road and it would likely diminish their home values, but can't help but laugh at the incompetence.