Final answer:
The bus companies would prefer the definition of the market for intercity bus service because it allows them to present themselves as dominant players in that market segment.
Step-by-step explanation:
The bus companies, Greyhound Lines, Inc. and Trailways Transportation System, would prefer the definition of the market for intercity bus service. This is because by defining the market as the 'market for intercity bus service,' they can present themselves as the dominant players in that specific market segment. This would allow them to have more control over pricing, competition, and market share within the intercity bus service industry.