I really don't know if they'd fit Cherry MX, I don't have any such board. If someone wants to gift me one so I can try, well I would graciously accept!
They work fine on a 6112884, with a little TI99/4A thrown in to get the correct legends on the number keys. I actually find this more agreeable to type on than the default keycaps on the 6112884. I am happy. The TI keys are sunken compared to the HPs. I'll see if this becomes a problem in practice. It's just a shame that I couldn't get more of the larger keys involved here; the TI just has no large keys besides right shift and the HP wasn't exactly flush with them as well, and while the "cursor fast" key might be the right width for left shift on the 6112884, the mounting scheme is subtly different, the HP has three cross-shaped holes, the IBM has one switch towards the right and one post towards the left that rides up into a simple cavity in the keycap, which bottoms out on a rubber o-ring on the post. It would have required physically modifying one of those items, and I am simply unwilling to make it so either the HP or the IBM won't go back to the way they were meant to be.
I don't have time for a teardown right now but I will see about later this week; I'll get there eventually, but for the meantime, this happened while I was swapping keycaps:
(It went back in fine)