@Ajit Sahane
1) xyz.com/regionname-r123456
2) xyz.com/cityname-c123456
3) xyz.com/maincategoryname_cityname-c123456
4) xyz.com/maincategoryname_regionname-r123456
-- all above are valid, unique and seo friendly links (note that links does not need to be user friendly as noone is going to remember link to category, city or region on none page). Number at the end is idenfitier of city/region.
Keep in mind that even url in format xyz.com/category,5/city,London/region,10/ is in seo friendly format. URLs cannot contain ? and & signs.
If you do not like how urls are generated, you can change it in permalinks setting or simply close your eyes.
For "duplicated" content (or duplicated urls):
- pages with no listings should be put to nofollow,noindex by theme in search.php
- pages those are duplicate (like /category,Car .... /car) should have canonical url generated by osclass
Osclasspoint.com runs on osclass and never got warning from google about duplicated content, bad urls or whatever impacting seo.
You just wasting time with these theories.