House Sparrows

Anybody had any experience of House Sparrows lining empty nestboxes for winter roosts? A contact of mine in the north east put up a terrace of boxes in September and has just noticed some of the holes with grass poking out, on checking them she found them lined with grass and a few droppings. She is sure they haven't been used for late breeding (September would be very late?) so assumes they must have been lined as a warm roost?