In my experience, even the authorities have only the vaguest clue about when future roadworks will take place.
My experience is based on occasions when they are mending the phone lines to my house (a roughly two-yearly event that involves temporary traffic lights). There are many sub-contractors and authorities involved and any of them can and do postpone the works at the drop of a hat. The previous time it was 5 weeks (during which I had no phone) before all their windows of opportunity happened to co-incide.