I work as a contract program at a large provider site that recently replaced their hospital and professional patient management/clinical systems with Epic.   In their old environment, the hospital billing was done by a third-party vendor while the professional billing was done with the same system that did patient management/clinicals.

They stayed with the incumbent billing vendor on the hospital side but now use Epic as their professional billing system.

I don't know the answer to the "why" part of the question.  Possibly because they are satisfied with the hospital billing vendor and wanted to lessen the impact of change and the retraining that would have been required. 

Yes, we use Meditech for everything.  It isn't an easy system to learn and it isn't intuitive in any part but it does do almost everything we need to do.  The reporting is the biggest pain for me.  I can't make anything come out of the system.

 I agree, I was recently trained at a hospital where they switched to EPIC and it was a difficult system to learn. I consider myself to be decent with computers, but working with EPIC was not an overly fun learning experience. I don't understand why things have to be so complicated...