Proterra also makes a Fuel Cell version of their bus and it would use the same UQM Powerphase150 electric motors. Since Fuel Cells are outrageously expensive, they probably won't be making many.
Even the Fuel Cell version may need Altair batteries, but presumably a lot smaller quantity per bus. (But the P.R. you linked doesn't mention using Altair batteries in the Fuel Cell version.) "...for incorporation into Proterra's all-electric and hybrid-electric buses."