I was researching the issue you describe here and found a way for you to report a problem with in accurate locations on the Maps app.
iOS 6: Using Maps
If Maps fails to display results, results are incorrect, locations are missing, or you experience any other issue while using Maps, you can report the issue:
- Tap Overview, then tap the lower-right corner of the display.
- Tap Report a Problem.
- Choose the appropriate issue description and follow the onscreen instructions.
All the best,