The period of the debris cloud interactions is about equal to the orbital period of Hubble's orbit. If the orbit was a different inclination but otherwise similar and so crossed Hubble's orbit, it would do so at two points and so the period would be half of the orbital period (it would also require extremely unlikely timing to get it to cross Hubble's orbit and actually hit Hubble at the crossing point, but if it did so at one it should do so at both.)
For it to then hit the ISS, at a far different altitude and inclination is even more problematic.
Yeah, it'd be every 180 minutes. There'd be two orbits, the circular 90 minute orbit of the ISS and an elliptical, 180 minute debris orbit that has a common perigee with the ISS but a farther out apogee. The debris would thus be moving faster at perigee and would be able to wreak havoc every second orbit of the ISS. Of course the chance of such coincidental orbits happening by accident would be insanely low; you'd need some explanation as to why the object that blew up was in that kind of orbit in the first place.
Actually ... if you imagine two debris fields spaced opposite in the elliptical orbit, or simply a debris ring, then you would have the devastation occurring every 90 minutes. It's even less likely trying to think of how this could happen accidentally, but you could certainly set up a situation like this intentionally.
