Also, and this is a genuine question (there may well be very good reasons for it), why not ground share with Histon, a ground that must meet minimum standards and is (I believe) rather nearer than Newmarket?
Always remember my one and only visit to Milton Road - Cambridge City v Merthyr in the Beazer Homes League (or whatever it was at the time) the day after Princess Diana's funeral had given us an unnecessary day off football.
Merthyr won 3-0 after their ex-Grimsby and WBA striker Tony Rees had got Cambridge reduced to ten men. Liked the ground very much - you had to walk through a science park (or some such) to get to it.
Histon already ground share with Cambridge University Press FC of the Eastern Counties League - presumably there must already be some sort of agreement in place with them, as I would be surprised if City hadn't approached Histon.