In some ways it's a relief that ExoMars' sensors will take weeks to commission; it's got cameras on board, including one which was intended to be able to take 5m/pixel images of Mars' surface from orbit. Pointing this at what's left of the upper stage could well produce some rather interesting data.

It'd also require ExoMars to be extensively reprogrammed at very short notice and risk bricking it, which is not something you want to do with a critical part of a billion-euro science program...