This is just a guess. Let's say I am one of the underdogs in the cell phone business. I happen to know that in today's job market an ad for a job (almost any job) can generate about 100 resumes - complete with name address and phone number or e-mail address.
I send all those high tech folks who applied for a high tech job an advertisement for my cell phone service and possibly some will actually buy my products and service.
It is completely legal and there is no one who can prove there was no real job. Unethical, you bet. Profitable, absolutely.
If I am lucky, people may even start a discussion about it and mention my company's name on some public job board. Free advertising! :)
Have you gotten any ads from them lately?