IR surely can be used in nighttime photography, but the result for me is not that exciting, because although man-made lightings do have quite a lot of IR light in it, it will appear (tendenciously) in one-two colors.. i prefer to shoot using regular DSLR during the nighttime because the result would be much better than using IR camera.
And, for that particular reason, the reason that indicates IR can be optimized during daytime only, IR shooting during nighttime is just not my preference.
Feel free to express yourself though..
