Google had made an announcement on Google+ that call extensions now support local forwarding numbers. Businesses can now show searchers local numbers, which may increase the chances of them calling your local business.
Here's what Google said, "starting today, ads with call extensions set up to use Google forwarding numbers can now show a local Google forwarding number, where available".
The local forwarding numbers will use the same area code as your business phone number or the local area code for same geographic region. These will only work for US businesses.
You can see the help documents to know more on how to set up the local numbers.Google AdWords Will Now Show Local Forwarding Numbers for Call Extensions!,