Hey dude, I like the idea and stuff, but NO city council on this planet will okay for you to put your own rails on some hill. Think of just a FEW of the legal issues. The city would have to assess your rails for safety, think of the waivers issue, theft...plus the fact that they know local hills offer this kinda thing already. Not to mention, most terrain where you would want to build (for in-run purposes) is considered 'family sliding hill' i'm sure and these rails would attract those evil snowboarders who the city fear will ruin, rape and plunder the family folk.
Doesn't waste your time writting to the city, they will not help you out, spend the time sessioning an urban or something. Atln. Canada has some of the best urban terrain in North America. Why spend days putting in a down-flat-down when you could just go session one?
More power to ya, but this is a wasted cause.