Everything Dent says is basically true, but you can still manage this. I know people who do it regularly. However, it takes some approximation, and this guy has to really ask himself "Why do this?" He should have a really good reason. "It seems like a good idea" is not a good reason.

The process involves taking advantage of the fact that each individual "job site" is relatively small, and earth curvature does not matter within the site itself. Therefore, you can calculate a "conversion factor" for each job. This is usually a number that is really close to 1, that lets you convert your job coordinates to state plane. The only way to determine this is to tie down known reference monuments on and near the site in your local coordinate system, and then use that information and the published state plane coordinates for the points to determine your "scale factor" for that particular job. You then need to scale the whole job by that factor. You can then place the result in your "state plane" drawing along with other jobs. Note that EVERY JOB will have a unique scale factor.

Also note that the result is only an approximation. As Dent says, lines and points from adjacent jobs will not come in exactly on top of each other. You can end up with a real mess, depending on what you're doing. So make sure this is REALLY the route you NEED to go down.