UAB is not building an OCS. Its downtown and I believe is operated by the city, UAB is just the primary tenant.
https://www.al.com/sports/index.ssf/2018/03/new_stadium_cements_survival_o.html
The stadium isn't just for UAB, obviously, but the Blazers will be the venue's first permanent tenant. UAB is signing a 20-year lease with the BJCC Authority to play there.