Each single user license allows for two activated installations. If your company bought a single user license they can allow it to be installed and activated on two machines. A condition of having it installed and acrtivated on two machines is that the suite can not be used on both machines at the same time.
As far as buying an additional license goes, Adobe no longer sells CS5.5 so that would not work for you anyways. If they did, it would be another separate license that would allow you to install and activate on two machines.
If your company purchased some form of volume license, that will be another story and how that works would have to be discussed with Adobe support directly.