We have the same issue with a couple developments that were platted over 20 years ago. The only way for us to resolve the problem is to finance the improvements and then setup a special assessment district to recover the costs. Taking this from another angle, the individuals that bought property should have had something in writing or contacted the city to get a copy of your development policy. We've had a number of people complain about the City not developing their streets, but the lack of a street is what made their lot such a bargain. Finally, some planning agencies require a bond or other assurance that the developer will properly install utilities and streets. You may want to see if such a document was recorded at the county, as this may provide some recourse if the developer still owns lots in the development.