That's weird because I used an 11-45 with RK05s running V7.
afaicr there was an informal distribution mechanism were you could get a bootable RK05 cartridge from another site so I suppose that's how they got it going.
So I've been digging around and there's another issue. A single RK05 is simply too small at 2.odd megabytes capacity. I assume you did have multiple RK05s in there and split up the filesystem. If so, then aiju's code would probably need other intensive modifications to support multiple of them.
They had a CDC disk pack type drive for the main filesystem (80 meg I think). I guess it is possible they bootstrapped it from a disk pack from another site with the same kind of drive, although that seems a little unlikely. Perhaps the interface was compatible with RL05, something like that. The machine did have multiple RK05s but I don't think they were used beyond boot and transferring data to other machines on campus.
afaicr there was an informal distribution mechanism were you could get a bootable RK05 cartridge from another site so I suppose that's how they got it going.