According to boxrec, Khan vs. Malignaggi and Victor Ortiz vs. Campbell are fighting at MSG on April 15th. It has HBO listed as carrying the fight.

HBO does not have the fight listed on their site though. As a matter of fact the only fights HBO has listed are

Devon Alexander vs. Juan Urango Mar. 6th

Pacquiao vs. Clottey Mar. 13th

Mayweather vs. Mosley May 1st