What about using expressions like когда рак на горе свистнет, "when the crayfish whistles on the mountain" (i.e., "when pigs fly") or пока жареный петух не клюнет в жопу, "until a roasted rooster will have pecked [someone] in the ass" ( i.e., no preventative measures will be taken until after something bad has already happened)??

So, with regard to your example about street-repairs, I think it would be correct to say:

В нашем городе отремонтируют дороги когда рак на горе свистнет.
"In our city, they will repair the roads when the crayfish whistles on the mountain." (i.e., never)

or:

В нашем городе не отремонтируют дороги пока жареный петух не клюнет в жопу.
"In our city, they won't repair the roads until a roasted rooster pecks them in the ass." (i.e., after a huge pothole causes a serious accident)

But of course, let's wait to see whether native speakers agree with this...

P.S. With the "rooster" expression, it's definitely okay to use задница ("butt") instead of the cruder жопа.