Congrats on your admission, desimba. I've posted about U-Mich's econ department many times; here is a recent thread on the subject. You can find more by using the search function.
The business econ students take first year math camp, micro, and econometrics with the econ PhD students -- everything except for macro. Those in my cohort are pretty well integrated into the class. They come to seminars, skit night, parties, etc. They also join study groups with econ students. They are spared taking the micro prelim, though! Ocasionally, there will be business econ students with very different expectations about the program than the econ PhD students (either about the level of course work, or about how classes are run), but those are idiosyncratic personality things, not anything systematic about the program.
I don't know much about the job placements for the IB-BE program, but the research I've seen students in that program present is solid.