Steve -
This is a 4.46 bug, but I have no reason to believe that it isn't still a problem in 4.6x. I have shipped several prefabbed PDC's from Strug Home to The Redoubt, along with six engineer regiments, and a small amount of each trans-newtonian resource. Once everything was in place I set the engineer regiments to assembling the prefabbed PDC's on the industry window of the economics screen. Everything appeared to be fine, with a completion date fourteen months in the future. However, after numerous months of game time I checked the progress of the job and noted that it appeared that no work had been completed on the job (amount remaining "1"), and that the completion date still fourteen months in the future. I advanced the time five days, and the amount remaining stayed the same, and the job completion date advanced five days. There are no error messages, or any notations on the event updates screen as to any problems.
To see just how far the problem extends, I cancelled assembly of the PDC and set the engineering regiments to construct 1 industrial capacilty. The info on the industry tab showed that it would take just under 1 year, as the cost was 120 and the six engineer regiments had an annual production of 121.5. However, after advancing the time five days, the screen showed no work completed and the estimated completion date advanced five days.
The engineering units appear to be non-functional.
Kurt