I did the MSt in IR, for which references from my employers highlighting my 'academic' work for them played a large part. However, the nature of my employment also indicated I was used to meeting deadlines, keeping to agreed timetables, working under pressure, providing accurate, well researched written work etc, so I had all the 'transferable skills' as well.
I had to show my transcript from my undergrad degree 20 years previously (which the Uni in question was able to provide immediately!) but did not have to get any academic reference from staff there.
I've subsequently gone on to do a PhD in IR, same location.