Can you use a company's page as the author for google authorship or does it have to be an actual persons google + account for it to work ?
I.e. could i have it showing in search results as "-by acme co" rather than "-by simon smith "
Yes. Mashable has a good rundown on setting up a G+ brand page and you can find out how to implement authorship information in this answer to "How do I get my Google+ picture to show up on Google searches?"