(CBS forensic series, 2000-)

Episode 1:10 Sex Lies and Larvae
A woman apparently abandons her car and disappears at a Las Vegas bus station. There is a brief sighting of two buses at the station.

Episode 2:18: Chasing the Bus
Set in Las Vegas; an MCI MCI-9 tour coach (bearing the number 5326) of the fictional Mojave Express line crashes on the way to Las Vegas:

During the investigation two identical vehicles are seen at the operator's maintenance facility. Another MCI-9 (I'd guess one of these two) undergoes testing at the lab:

In the last scene at a truck stop a motorcoach of Antelope Lines is seen leaving, and an unidentified Setra coach arrives:

(observations by Carlos Wallberg and myself!)