How will I benefit my company by studying an MBA? How companies will
benefit themselves by offering tuition assistance to their employees?
I don't want to know how an MBA will benifit the employees on their
careers, I already know that, but how the companies will benefit from
it.

On one side company gets an employee armed with new methods and
insights, which will make them more efficient, allow to increase
revenues, decrease cost, do things faster, communicate more clearly,
etc.

On the other side, an MBA froma decent school means meeting a lot of
other businessmen from different industries and countries, so the
company could benefit from having an employee with such a wide
"network" of people they know.

Thanks for your comment,
I am trying to find some kind of study that proves how having a MBA
will make you a better employee for the company.
The reason behind all of this, is that my direct manager doesn't seem
to be eagerto approve the tuition help because he doesn't see any
benefit.
I am trying to prove him wrong based on some empiric data.

I found one UK study:

The Value of Business and Management Education:
http://www.henleymc.ac.uk/henleyres03.nsf/files/CML_0205_ValueOfBusiness.pdf/$FILE/CML_0205_ValueOfBusiness.pdf

Might help your case.

Some other (maybe) related scholarly docs:
http://scholar.google.com/scholar?q=benefits%20of%20an%20MBA%20to%20company&hl=en&lr=&safe=off&oi=scholart

Good luck,
LP