Google local search results
Generally companies that serve customers at a physical address will find it easier to rank within the local search results compared to that of a companie that does not have an address but serves customers in X miles. This isn't to say they can't rank but it requires a lot more citiations, social mentions, backlinks and authorithy to do so.
Telling Google places/plus that you serve multiple areas
Google uses Google Places and Plus to verify your business and this is a HUGE! factor in getting your site to return in local results. If you haven't already you should tell Google how many miles you provide services too, this doesn't necessary mean your rank within those areas because you may find other competitive businesses with better rankings.
If you have multiple offices where the customer is served as such then your find it easier to rank, this is because of several reasons such as trust and providing customers with the very best in search results, after-all some customers would rather be served by local companies and not neighboring companies. But with this said this isn't always the case.
Example of keyword without area
Some niches even have just the keyword enabled for local searches and as you can see from the image below multiple physical addresses being returned and by major competitors, and if you look closely you can see (F) doesn't even have an address this is because they checked do not serve customers at address button, But as you can see there's no neighbor companies.
The right signals
Its not a requirement that you have a psyical address in the area you serve but it does help because links, social mentions and citations will have the keywords of your area. To increase your rankings for local searches in the targeted area you need to increase on site authority, trust and various other signals. When adding your site to Yelp, Yell, BT and so on you should write somewhere on the page that you serve X area, Google can then tag your site as relevant to that area.
Another way is and I don't recommend it but many businesses do it, is they get a friend or family member who lives in the targeted area, you get the address verified on Google Plus and Places, then disable the address by clicking we do not serve customers at this address. This will then become easier to rank in that area, but again I don't advise it, Google will likely clamp down on that.. My recommendations is to increase the area you serve and include keywords on all citations pages.