Else if you really want the near plane you could take a look into my Shadow shader code, i reconstruct the entire Projection Matrix there.

This is how i retrieved the camera boundary from AGK:

CameraVectorID=CreateVector3(GetCameraX(1),GetCameraY(1),GetCameraZ(1))
NearLeftTopVectorID=CreateVector3(Get3DVectorXFromScreen(0,0),Get3DVectorYFromScreen(0,0),Get3DVectorZFromScreen(0,0))
FarLeftTopVectorID=CreateVector3(GetVector3X(NearLeftTopVectorID)*Shadow_Distance#,GetVector3Y(NearLeftTopVectorID)*Shadow_Distance#,GetVector3Z(NearLeftTopVectorID)*Shadow_Distance#)
GetVector3Add(NearLeftTopVectorID,CameraVectorID)
GetVector3Add(FarLeftTopVectorID,CameraVectorID)
NearRightTopVectorID=CreateVector3(Get3DVectorXFromScreen(GetDeviceWidth(),0),Get3DVectorYFromScreen(GetDeviceWidth(),0),Get3DVectorZFromScreen(GetDeviceWidth(),0))
FarRightTopVectorID=CreateVector3(GetVector3X(NearRightTopVectorID)*Shadow_Distance#,GetVector3Y(NearRightTopVectorID)*Shadow_Distance#,GetVector3Z(NearRightTopVectorID)*Shadow_Distance#)
GetVector3Add(NearRightTopVectorID,CameraVectorID)
GetVector3Add(FarRightTopVectorID,CameraVectorID)
NearLeftBottomVectorID=CreateVector3(Get3DVectorXFromScreen(0,GetDeviceHeight()),Get3DVectorYFromScreen(0,GetDeviceHeight()),Get3DVectorZFromScreen(0,GetDeviceHeight()))
FarLeftBottomVectorID=CreateVector3(GetVector3X(NearLeftBottomVectorID)*Shadow_Distance#,GetVector3Y(NearLeftBottomVectorID)*Shadow_Distance#,GetVector3Z(NearLeftBottomVectorID)*Shadow_Distance#)
GetVector3Add(NearLeftBottomVectorID,CameraVectorID)
GetVector3Add(FarLeftBottomVectorID,CameraVectorID)
NearRightBottomVectorID=CreateVector3(Get3DVectorXFromScreen(GetDeviceWidth(),GetDeviceHeight()),Get3DVectorYFromScreen(GetDeviceWidth(),GetDeviceHeight()),Get3DVectorZFromScreen(GetDeviceWidth(),GetDeviceHeight()))
FarRightBottomVectorID=CreateVector3(GetVector3X(NearRightBottomVectorID)*Shadow_Distance#,GetVector3Y(NearRightBottomVectorID)*Shadow_Distance#,GetVector3Z(NearRightBottomVectorID)*Shadow_Distance#)
GetVector3Add(NearRightBottomVectorID,CameraVectorID)
GetVector3Add(FarRightBottomVectorID,CameraVectorID)