Alaa,
The identify task will not return the full joined field name. You will always get FKPROJECT_ID instead of ALDARGIS.PLANNING_PHASE.FKPROJECT_ID
Tony,
Yep that is exactly what happens. So all you have to do is define the fields aliases in ArcCatalog for the individual feature classes or in ArcMap if you only want those to be defined for that particular map service.