Charles.INCarey - Not necessarily true... If that company had IT Personnel that employed the Volume License way of installing Windows (Legitimately I might add, Open license or otherwise) every machine could have the same key and still be legit.
Also, Every big box OEM company has a special method to Bypass the Activation (Dell, HP, Lenovo, Acer, etc). There is a special BIOS file that when used in conjunction with a certain Windows key does not require it to be activated, it just activates itself. Thus if your machines are, like Carey said, OEM type machines they would also report the same key, unless they've been reinstalled using non-oem disks.
It's not always a good move to just base off of Product Keys.