Hi Anupam -
i do recommend getting in touch with GBCI about these questions through their 'contact us' form : http://www.gbci.org/org-nav/contact/Contact-Us/Project-Certification-Que.... It doesn't sound like the gas station will be eligible - check out the Minimum Program requirements here: http://www.usgbc.org/DisplayPage.aspx?CMSPageID=2102. It is possible to streamline the documentation of site credits if you have multiple buildings on one site - the GBCI folks will be able to help you with this.
Please be aware that we are working on a new application guide for multiple buildings to address these kind of situations. Though there is not a timeline for its release, we are working hard on it and will get it out there as soon as we can!
Cara Mae