You can e-mail Disney directly about a specific company. My husband works for Delphi and I wasn't sure if we would be able to use the lounge, but I e-mailed Disney and within a day they sent a very nice reply stating that yes, we could use it along with our guests.
The receptionist is very, very nice and has a great sense of humor as well. When we were there over spring break, we buzzed to be let into the elevator and she came over the speaker and said "How many are in your party?" When we answered 10, she very casually replied, "I'm terribly sorry, but that's 8 too many." We were shocked because of Disney's e-mail. But then we realized it was April 1 and she was just having fun at our expense.
It was very busy during spring break and although we could enter the lounge as often as we wanted, they would only let us go to the front of the line once per day. It was still well worth it!