We have a litter tray out in the garden and ours have been pelting out there to poo - but not nearly as often as they do usually - or sneaking out under some bushes. We know - cos we've seen - that just outside the back door, they are going under the table for a wee. We are going to have to disinfect when the snow melts! They're not eating quite so much, perhaps input = output at the moment.
I'm more worried about their drinking as they won't drink in the house, but their usual birdbath is frozen solid, and they keep kicking over their indoor waterbowl!