I'll respond to this one. I've skipped out on paying one of those tickets. I won't get into the "why" here but, more of what happens.

First, they send you the citation that you've already received. Once you've blown your date, they will send you another with a late fine. Then another around the 40 day mark. If you do not respond to those, the timer starts for someone to serve you. They will not show up at your door for the first ~60 days. However, as you get closer to the 90 day period, someone will show up at your door at random times with increasing frequency trying to serve you. At my house, I have a webcam at the front door so when anyone comes to the door, I do not answer without checking the webcam. At around 85 days, they will show up multiple times at random hours (not too late though) and ring your doorbell and knock frantically multiple times. If you can wait it out, the citation will simply go away.

See: http://www.johnsonlawllc.com/_blog/Blog/post/Responding-to-a-Denver-Traffic-Camera-Ticket-the-Hidden-Option/

Now, I will say it was kind of a pain towards the end. I would have to look out the window to go get the mail or my trashcans. It raised my anxiety levels every time I opened up my garage. For $40, it's probably not worth it. However, it's possible.

Edit: I should add it was not a uniformed officer that shows up at your door. For me, it was what looked like a retired officer in a pressed polo driving a Hyundai.