If you are Fox Sports 1 ....... Thursday 3-September-2015 is a big opportunity. Fox Sports 1 typically trails ESPN (by a lot) in the ratings, but in 20 days it's the start of the football season and they have a game which compares favorably in terms of public interest vs. those games that ESPN will be showing (UNC v. South Carolina and Minnesota v. TCU).
Of course, Fox Sports 1 has relatively low visibility with consumers, at least as compared to ESPN. There are probably a lot of people who have no idea Fox Sports 1 has the Michigan vs. Utah game. This bus is surely one of the multiple marketing activities Fox is using to promote the fact that they have a premiere TV game in 20 days. And if Fox Sports 1 out-rates ESPN in 20 days, that's a heck of a big win for them.
So ................. that's my logical explanation for the promotion on the side of a bus. I'm sure others here will go with the conspiratorial explanation. Fair enough.