OK I'll bite after doing mergers in the past. This perspective is from a corporate perspective.
The main concern is of "culture". This is the biggest issue, can the two parties work together. Once you get past culture, is the technology compatibility? Do you have synergies between the businesses.
Usually when you have a merger, the people who are acquired stay long enough to find a new job or wait until incentive packages pay out.
Mergers are all about position and pay. If the merged employee doesn't like it they leave. the company that merges the other company has total control.
With government its different. Not sure if you can really compare.