Sure there is - there's forfeit rules baked into the Premier League rulebook.
If City make the request to postpone and we refuse it, the Premier League has to act further or it reverts to standard forfeit rules.
It'd have been better that way too, as it'd have codified the rule. Nobody has a clue what constitutes a serious enough outbreak for a game to be postponed from what I can tell - it's being winged. So there's every possibility in the return fixture we ask for a suspension of the game and the Premier League refuses because we had one less positive test than City had, and we'd have no leg to stand on.