I was mainly refering to your, "The last group they will ask for a opinion from will be the unions." comment.
Unions alone have not stopped a merger, you are correct. But its because they represent 1 side of the issue. Employment. Job oppurtunity is 1 of the many factors the government looks at before approving mergers. Respected labor unions are often asked to weigh in on the topic. Unions, consumer groups, and other orgs help the FCC make their decision.
You question my source. Does it not matter these are court papers with docket numbers.