They're MTB rims, but still reasonably narrow, I think with some cutting and re-positioning of the rear brake bridge and the small bridge where the fender attaches to at the front, they shoud fit. I'm thinking.....Rohloff??......nah, maybe Nexus or S/A 8 speed.
Anyways, I have a 24" frame very similar to the R20 that I can use if it isn't possible, less hassle with BB thread and width, threaded steerer, more cockpit room etc.