An enterprising developer going by the name of Senocular has managed to use the google map system to display a scrolling, zoomable map of Paradise City that allows you to overlay a variety of the challenge content in the game, ie. race routes, gas stations etc. It's pretty cool, check it out below. I've also posted a link to the developer's blog so you can read about how he did it!
Burnout Paradise Interactive City map
Developer Blog