I believe there is other hardware running EFI as it was developed by Intel, but there is a version or two of Winblows that won't run on it. I forget which.
The reason M$ have corporate IT in its pocket, is because it has the buyers in its pocket. It works like this:
Company hires IT guy. Who to hire? Everyone uses Winblows so we'll get a guy with an M$ certificate.
What kit do we buy? Lets ask the IT guy we hired.
What kit is (s)he going to choose? Not one they don't have a certificate for thats for sure. And when the boss sees how cheap this hardware is, they'll be impressed. They don't expect to get much leeway over the price of the software, since they have to buy Winblows and OFfice, and they cost what they cost. So thats labelled as a 'necessary expense'.

Even those companies lucky enough to have a guy who knows about Macs, is going to take one look at his/her quotations and say: "You want us to spend how much on hardware?!"
Asking the people who sign the cheques to see past the bottom line hardware bill is a battle Apple have been fighting for years.
Funny thing is when you ask them why they don't pay a Mercedes salesman to tell them what company vehicles they need and how many they should buy, and what make they should be, they finally start to get your point.