Here was GE's reply when I asked them directly:
So, it looks like I'll be installing multiple ballasts for the multiple T8 bulbs.You apparently had a question for GE regarding the compatibility of our electronic GE632MAX-H90 ballast with F15T8/BL lamps. The answer is no...this is a preheat lamp and requires an equal type ballast. Best bet is Advance.
Mike: I read that CFL blacklights are made the same way as those old-school el-cheapo incandescent novelty blacklights, in that they're a cheap filter applied over a full-spectrum light. In contract, the blacklight fluorescent bulbs emit the desired wavelengths directly.
30-60 minutes is too slow for my needs. My normal cyanotype printing time (Mike Ware's new cyanotype recipe and Sacramento's summer sun) is 4 minutes ... I know that my time is going to increase, but a 60-minute time is too long!