I think it depends more on the grades than anything.
I wouldn't say it's more employable than say an English Literature degree or a degree in History.
With a business management degree, you're technically going for jobs that allow for any degree i.e. you can't really go into medicine or beome a scientist with it. Whilst you will learn a bunch of management theory and techniques that would prove useful within any business environment, employers tend to require you to learn from the ground up and do things their way, as if you never had learnt anything about business.The degree can prove useful if you decide to start your own business, but I wouldn't say it's more employable than any other degree.
I can't really say whether employers have a preference for management graduates from particular universities. If they do, I think it has more to do with the university than the actual degree.